Document:

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                                                                    Exhibit 10.6

AutoNation                                                  PETER C. SMITH
                                                         Senior Vice President
                                                            Human Resources

                                 April 18, 2000

Mr. Craig Monaghan
146 Armand Road
Ridgefield, CT  06877

Dear Craig:

         Welcome to AutoNation, Inc.! This letter will confirm our offer of
employment as follows:

POSITION:                           Chief Financial Officer, Senior Vice
                                    President, reporting to the Chief Executive
                                    Officer of the Company, Michael Jackson.

START DATE:                         May 8, 2000, or a mutually agreed upon date.

SALARY:                             $17,307.69 payable bi-weekly ($450,000
                                    annualized)

SIGNING BONUS:                      Upon joining AutoNation, Inc. and your
                                    appointment by the Board of Directors as a
                                    Senior Executive, you will also receive a
                                    $100,000 signing bonus, less applicable tax
                                    withholding.

YEAR 2000 ANNUAL BONUS:             You will be eligible for a Year 2000 bonus
                                    representing up to 50% of annual base salary
                                    ($450,000), from January 1, 2000, in the
                                    event the Company's earnings per share (EPS)
                                    equals or exceeds .90 per share, and subject
                                    to approval or modification of the Board of
                                    Directors.

RELOCATION:                         The Company will provide you with relocation
                                    assistance in moving you and your personal
                                    property to our area. Attached for your
                                    review is a copy of the Relocation Policy.
                                    You are eligible for Tier 4 benefits. Should
                                    you voluntarily terminate employment, other
                                    than for Good Reason (as defined in the
                                    attached rider) on or before one year of
                                    employment, a pro-rated share of all
                                    relocation

<PAGE>   2

Mr. Craig Monaghan
04/18/00
Page 2

                                    reimbursements must be repaid to the Company
                                    pursuant to the policy.

STOCK OPTION PLAN -                 The Company intends to give you an Initial
INITIAL GRANT:                      Grant of options to acquire 350,000 shares
                                    of AutoNation, Inc. common stock. This grant
                                    is subject to approval by the Board of
                                    Directors. The strike price will be the
                                    closing price of AutoNation, Inc. common
                                    stock on the last trading day prior to your
                                    date of employment. As stated above, under
                                    the provisions of the Company's Employee
                                    Stock Option Plan (the "Plan") stock options
                                    vest twenty-five percent (25%) per year
                                    during your term of employment beginning
                                    with the date of your grant. This Initial
                                    Grant will represent your entire stock
                                    option grant for the year 2000, and as such,
                                    you will not be eligible to receive any
                                    additional stock option grants during 2000.

STOCK OPTION PLAN -                 Subject to the discretion of the Board of
FUTURE GRANTS:                      Director's Compensation Committee, in 2001
                                    and future years, you may participate in the
                                    Company's Plan for options awarded
                                    commensurate with your position. The terms
                                    and conditions of the Plan are subject to
                                    change from time to time as determined by
                                    the Board of Directors.

SEVERANCE:                          At any time during your employment, the
                                    Company has the right to terminate the
                                    employment relationship and to discharge
                                    your employment and you may also terminate
                                    the employment relationship for any reason
                                    or no reason at all. Upon termination of
                                    your employment by the Company at any time
                                    other than for cause, or upon termination of
                                    your employment for "Good Reason" at any
                                    time, in each case as defined in this letter
                                    agreement, you will be eligible to receive
                                    an amount equivalent to eighteen (18) months
                                    of your initial annual base salary,
                                    $450,000, (i.e., a gross total severance
                                    payment of $675,000) less applicable taxable
                                    withholding. (See "Good Reason" rider
                                    attached). The severance payments shall be
                                    disbursed as salary continuation in equal
                                    bi-monthly installments in accordance with
                                    the Company's normal payroll practices and
                                    shall be contingent upon your execution of a
                                    general waiver and release of all claims.
                                    You shall have no obligation to obtain
                                    alternative employment during the severance
                                    period. The severance payments will not
                                    discontinue OR BE DECREASED IN ANY WAY as a
                                    result of your obtaining employment
                                    during the severance period, except if you
                                    become re-employed with AutoNation or any of
                                    its subsidiaries. Additionally, during the
                                    severance period the Company will provide
                                    you with a COBRA subsidy, representing the
                                    cost of your COBRA premium,

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Mr. Craig Monaghan
04/18/00
Page 3

                                    should you be eligible for and elect
                                    continuation of the Company's group health
                                    and welfare benefits plans. Stock option
                                    vesting will cease on the last day of
                                    employment, thus vesting will not continue
                                    during the severance period; provided,
                                    however, that you shall have 60 calendar
                                    days after the termination of your
                                    employment to exercise all vested stock
                                    options. In the event the Company ceases
                                    severance payments in breach of the general
                                    waiver and release of claims, you will be
                                    released from the non-compete restrictions
                                    within the Confidentiality and
                                    Non-Competition Agreement. Similarly, in the
                                    event you materially breach any of the
                                    covenants of the general waiver and release
                                    of claims or any provision of the
                                    Confidentiality and Non-Competition
                                    Agreement, in addition to any remedies and
                                    damages that may be available to the
                                    Company, the Company will cease all
                                    severance payments and benefits.

                                    If your employment is terminated for cause
                                    you will be paid that portion of the salary
                                    prorated through the date of termination,
                                    and the Company will have no further
                                    obligations. For purposes of this letter
                                    agreement, termination for "cause" shall
                                    mean a termination of your employment by the
                                    Company as a result of (i) your failure or
                                    refusal to perform the material duties and
                                    responsibilities required by the Company to
                                    be performed by you which are consistent
                                    with your position as Chief Financial
                                    Officer of the Company (provided that you
                                    are notified in writing of such failure or
                                    refusal and do not cure such failure or
                                    refusal within a reasonable period of time);
                                    (ii) your gross negligence or willful
                                    misconduct in the performance of your
                                    duties; (iii) the commission of an act of
                                    dishonesty affecting the Company or the
                                    commission of an act constituting common law
                                    fraud or a felony; or (iv) the commission of
                                    an act causing material damages to the
                                    Company (other than as a result of good
                                    faith exercise of your business judgment) or
                                    your following the directions of the CEO of
                                    the Company or the Board of Directors.

BENEFITS:                           You will be eligible to participate in the
                                    Company's group health and dental benefit
                                    programs effective on the first day of the
                                    month coincident with or following the
                                    completion of thirty days service.

DRUG SCREENING:                     This offer is contingent upon the successful
                                    completion of the Company's hair analysis
                                    drug screening process. Please contact Tracy
                                    Hamm at (954) 769-6746 so that she may
                                    arrange an

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Mr. Craig Monaghan
04/18/00
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                                    appointment at a clinic for the purpose of
                                    collecting a small hair sample for testing.

CONFIDENTIALITY AND                 Employment is contingent upon your signing
NON-COMPETE                         the Company's Confidentiality and
AGREEMENT:                          Non-Compete Agreement.

This letter along with the Company's Confidentiality and Non-Compete Agreement
represent the full and entire agreement of employment. Moreover no one in the
organization, other than the Chief Executive Officer ("CEO"), has the authority
or legal ability to modify the terms of this Agreement. The CEO can do so only
if it is done specifically in a written agreement. The position of Senior
Executive and the remuneration are subject to approval and/or modification of
the Company's Board of Directors. Please confirm your acceptance of this offer
by signing in the space provided below and then return one original signed copy
to me as soon as possible.

We look forward to having you join our team.

Sincerely,

/s/ Peter C. Smith
-------------------------------
Peter C. Smith

ACCEPTED:

/s/ Craig Monaghan
-------------------------------
Craig Monaghan

        April 19, 2000
-------------------------------
Date

Attachments:

(1)  Amended and Restated 1998 Employee Stock Option Plan
(2)  Confidentiality and Non-Compete Agreement
(3)  Good Reason Rider

<PAGE>   5
Mr. Craig Monaghan
04/18/00
Page 5

                                GOOD REASON RIDER

For purposes of this letter agreement, "Good Reason" shall mean a voluntary
termination of your employment as a result of (i) a material change by the
Company in your authority, duties or responsibilities which would cause your
position with the Company to become of materially less responsibility and
importance; (ii) any decrease in your base salary by the Company, and/or (iii)
during the first three (3) years of employment, your relocation by the Company
without your consent to an area outside of South Florida.AMENDMENT TO MARKETING AND DISTRIBUTION AGREEMENT

           The effective date of this Amendment will be July 12, 2000.

For good and valuable  consideration,  the receipt and  sufficiency  of which is
hereby  acknowledged  and confessed,  the parties to that certain  Marketing and
Distribution  Agreement,  effective  date December 31, 1997,  and its associated
extensions  and  amendments  (hereinafter  collectively  called the  Agreement),
between the ORTHOLOGIC  CORP.  (OrthoLogic)  and CHRYSALIS  BIOTECHNOLOGY,  INC.
(Chrysalis),  hereby  agree to amend the  Agreement in the  following  respects,
to-wit.

WHEREAS,  it is the desire of  OrthoLogic  and Chrysalis to expand the territory
for OrthoLogic  marketing and distribution of Chrysalin(TM) for fracture healing
to worldwide and to license worldwide  marketing and distribution rights for use
of Chrysalin(TM) in other orthopedic hard tissue applications, and

WHEREAS,  it is the desire of Chrysalis to grant and of OrthoLogic to acquire an
Option to license  orthopedic soft tissue  applications for worldwide  marketing
and distribution,

NOW  THEREFORE,  the parties hereby agree to amend the Agreement as follows with
reference to specific numbered items within the Agreement:

                            I. BACKGROUND AND PARTIES

1.1     CHRYSALIS.  Chrysalis  BioTechnology,  Inc.  ("CHRYSALIS") is a Delaware
        corporation,  having a principal place of business at 2200 Market, Suite
        600, Galveston, Texas 77550.

1.2     ORTHOLOGIC.  OrthoLogic Corp.  ("ORTHOLOGIC") is a Delaware corporation,
        having a principal  place of business  at 1275 West  Washington  Street,
        Tempe, Arizona 85281.

PARAGRAPH  2.7 OF THE  AGREEMENT  IS HEREBY  REPLACED  WITH THE  FOLLOWING:

                           II. ADDITIONAL DEFINITIONS

2.7     "FIELD OF USE"  shall  mean the use of the  Technology  Rights in one or
        more of the indications described in paragraphs  2.7.1-2.7.3 below under
        the terms and conditions of this Amendment.

2.7.1   "ORTHOPEDIC  FRACTURE  INDICATION"  shall be limited to the human use of
        the  Technology  Rights in  connection  with the treatment of fractures.

2.7.2   "ORTHOPEDIC HARD TISSUE  INDICATIONS"  shall be limited to the human use
        of the Technology Rights in connection with repair, grafting, or filling

************Text has been omitted pursuant to a confidentiality request. Omitted
text has been filed with the Securities & Exchange Commission.

                                                                          Page 1
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        of gaps in bone  that  may  result  from  trauma,  non-unions,  surgical
        removal of bone, or need to fuse two or more bone segments.  Thus, these
        indications  will include  treatment of segmental bone defects and spine
        fusion.  Excluded uses of the Technology Rights shall include, but shall
        not be limited to, dental and oral applications.

2.7.3   "ORTHOPEDIC SOFT TISSUE  INDICATIONS"  shall be limited to the human use
        of the  Technology  Rights in  connection  with  treatment and repair of
        damage  to  meniscus,  cartilage,  tendons  and  ligaments,  coating  or
        preparation  of  bone or  joint  implants,  and to  treatment  aimed  to
        directly affect disk repair.

PARAGRAPHS 2.11 AND 2.12 ARE ADDED AS FOLLOWS:

2.11    "TERRITORY"  Worldwide for (1) currently  licensed  Orthopedic  Fracture
        Indications,  (2) Orthopedic Hard Tissue Indications, and (3) Orthopedic
        Soft Tissue  Indications.  OrthoLogic's right to market products outside
        of the United  States  ("International  Rights") is based on  OrthoLogic
        meeting  the  following  conditions.   Failure  to  meet  the  following
        conditions would lead to forfeiture of all International  Rights for all
        applications within the Field of Use.

2.11.1. OrthoLogic  shall elect a  "Marketing  Partner"  based on the  Marketing
        Partner's qualifications, to include significant international marketing
        and sales  capability to orthopedic  products along with the ability and
        resources to rapidly initiate clinical trials in Europe and Asia.

2.11.2. ************

2.12    "RIGHTS"shall  mean the rights described in paragraphs  2.12.1 to 3.12.3
        below.

2.12.1  "RIGHT TO MARKET AND  DISTRIBUTE"  OrthoLogic and its Marketing  Partner
        shall have the Right to Market and Distribute  products within the Field
        of Use in the Licensed  Territory.  2.12.2 "RIGHT TO LIMITED END-PRODUCT
        MANUFACTURE"  OrthoLogic and its Marketing  Partner shall have the Right
        to undertake Limited End-product Manufacturing as per the Agreement, but
        not  the  right  to  manufacture  Chrysalis  peptides  (except  for  the
        allowances  in Section  IX).  2.12.3  "RIGHT TO  DISTRIBUTE  THROUGH 3RD
        PARTIES"  OrthoLogic or their Marketing  Partner shall have the right to
        distribute  products  for use in Field of Use in the  Territory  through
        third party distributors subject to the terms of 2.11. As per Agreement,
        all  sales  and   distributions  by  Marketing   Partner  or  3rd  Party
        distributors  will be treated for royalty  purposes as if they were sold
        directly by OrthoLogic.

          PARAGRAPH IV OF THE AGREEMENT IS HEREBY MODIFIED AS FOLLOWS:

************Text has been omitted pursuant to a confidentiality request. Omitted
text has been filed with the Securities & Exchange Commission.

                                                                          Page 2
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                         IV. OPTION GRANTS AND PAYMENTS

(e)(i-iii)-Unchanged.

(e)(iv) Within 3 days of the Effective Date of this  Agreement,  OrthoLogic will
pay $2 million by direct wire transfer to Chrysalis for the exclusive  Rights to
Chrysalin(TM)  for  Orthopedic  Hard Tissue  Indications  within the  Territory,
subject to the  conditions  in  Sections  2.11.1  and 2.11.2 and  payment of the
milestone payments herein.

(e)(v) Upon execution of this Amendment,  OrthoLogic will initiate an aggressive
development  program for  Chrysalin(TM) use in segmental bone defect filling and
spine fusion  indications in  collaboration  with  Chrysalis.  OrthoLogic  shall
pursue the following  milestones with Reasonable Efforts, and make the following
payments to Chrysalis  upon the  occurrence  of the events set forth below or to
extend the time for  achieving  the events,  so long as  OrthoLogic,  one of its
Affiliates,  or a sublicensing  partner, is still proceeding with the license or
licenses contemplated by each such payment.

         SPINE FUSION MILESTONES:

         1)       ************
         2)       ************
         3)       ************

         OTHER ORTHOPEDIC HARD TISSUE INDICATION MILESTONES:

         4)       ************
         5)       ************

(e)(vi)  Upon  execution of the  Amendment,  Chrysalis  will grant  OrthoLogic a
************ option for rights to Orthopedic Soft Tissue Indications. OrthoLogic
will have the right to execute its Option at any time within ************ of the
Effective Date of this Amendment by making a ************  payment to Chrysalis.
************ Upon exercise of the option for Orthopedic Soft Tissue Indications,
OrthoLogic will initiate an aggressive  development  program for at lease one of
the Orthopedic Soft Tissue Indications in collaboration with Chrysalis.

If  OrthoLogic  exercises  its option for the rights to  Orthopedic  Soft Tissue
Indications,  then it shall be  responsible  for the  payment  of the  following
milestones to Chrysalis:

         1)       ************
         2)       ************
         3)       ************

(e)(vii) If OrthoLogic retains its International Rights, subject to the terms of
2.11,  OrthoLogic and its Marketing Partner will pursue with Reasonable  Efforts
the initiations of clinical trials in Europe

************Text has been omitted pursuant to a confidentiality request. Omitted
text has been filed with the Securities & Exchange Commission.

                                                                          Page 3
<PAGE>
and Asia and other  steps  required  to  obtain  regulatory  approval  to market
products for Fracture  healing,  Orthopedic Hard Tissue,  and (if exercising its
option)  Orthopedic  Soft Tissue  Indications  in Europe,  Asia, and other major
markets  within  the  Territory.  The  following  milestones  will be paid  upon
achievement of such marketing approvals.

         a)       ************
         b)       ************
         c)       ************

(f)  unchanged.

(g)  deleted.

(h);(i)  unchanged.

(j) OrthoLogic  will not promote and will use  reasonable  efforts to discourage
the use of any Chrysalis  Product for Indications  outside of the licensed Field
of  Use.  It  will  also  use  reasonable  efforts  to  insure  that  commercial
embodiments or  formulations  using  Chrysalis  Product will be so formulated to
focus the product use for the  licensed  Indication.  Chrysalis  will have input
into all  formation  decisions  whether  or not  Chrysalis  is  involved  in the
manufacturing of the final formation.

PARAGRAPH 5.2 IS ADDED AFTER ROYALTY RATE TABLE AS FOLLOWS:

5.2  CATEGORIES OF NET SALES.  For the purpose of  calculating  royalties due to
Chrysalis  if  OrthoLogic  exercised  its option for Rights to  Orthopedic  Soft
Tissue  Indications all sales of products for Orthopedic Soft Tissue Indications
shall  be  separated  from  sales  of  Fracture  and   Orthopedic   Hard  Tissue
Indications. ************

************

In the event that a given product is sold for  indications  in both  categories,
its sales will be  calculated  in total in the category that has the lower total
Net Sales for the royalty period.

PARAGRAPH 5.2 BECOMES 5.3:

SECTION "VI" IS AMENDED AS FOLLOWS:

6.1 REPORTS. Last sentence to end . . . . specified by Sections 5.1 through 5.3.

PARAGRAPH 8.2 IS AMENDED TO ADD:

************Text  has been omitted pursuant to a confidentiality  request to the
Securities  and  Exchange  Commission.  Omitted  text  has been  filed  with the
Securities and Exchange Commission.

                                                                          Page 4
<PAGE>
          a)   If OrthoLogic or its Marketing Partners chooses to have Chrysalis
               provide  Chrysalin in a commercial  formulation  that  includes a
               matrix,   encapsulation,   or  specific   delivery   vehicle  for
               Fractures,  hard  Orthopedic  Tissue  or Soft  Orthopedic  Tissue
               Indications, an additional component to the transfer cost will be
               added  to  cover  the  additional  manufacturing  cost of the new
               formulation,************.

PARAGRAPH XVI "GENERAL" IS RENUMBERED AS PARAGRAPH XVII.  THE NEW
PARAGRAPH XVI IS AS FOLLOWS:

                           XVI. INTELLECTUAL PROPERTY

It is  anticipated  that  development  programs  may result in the  creation  of
intellectual property (IP) based on usage, dose, and/or specific formulations of
Chrysalin(TM)  or related  peptides or Technology  Improvements.  Chrysalis will
retain rights to any and all patents  resulting from development  programs using
TP508 or related peptides regardless of inventorship.  Where such patents extend
the exclusive  right to manufacture,  sell, or use TP508or related  peptides for
Orthopedic  Indications in the Field,  the  additional  patent  protection  will
likewise  extend the term of the original and amended  agreement and obligations
of  OrthoLogic,  its  partners  or  successors,  to  purchase  TP508 and related
peptides from Chrysalis and pay Royalties to Chrysalis.  In addition,  Chrysalis
will retain the following rights:

1.   SOLE OR JOINTLY DEVELOPED IP. Any and all patents resulting from IP jointly
     developed by Chrysalis  (or  Chrysalis/UTMB)  personnel  and  OrthoLogic or
     OrthoLogic  Partner  scientists  will be  assigned to  Chrysalis  (or UTMB)
     without fee and will be filed and prosecuted  either by or in consultations
     with Chrysalis IP Counsel.

2.   ORTHOLOGIC (OR PARTNER) IP (NO CHRYSALIS/UTMB INVENTORSHIP). All inventions
     related to the Chrysalin(TM)/TO508  technology will be promptly reported to
     Chrysalis. Any resulting patents related to or contributing to products for
     Licensed Indications will be assigned to Chrysalis without fee. Any patents
     resulting  from IP that  uses the  Chrysalin(TM)/TP508  technology,  but is
     specific to applications  outside of the Licensed  Indications may be owned
     and  patented  by  OrthoLogic  or Partner,  but right of first  refusal for
     licensing  such new IP will be  granted to  Chrysalis.  The  assignment  of
     patents  alone  under  this  condition  would  not  give  Chrysalis  use of
     OrthoLogic  or Partner  proprietary  matrix or  delivery  products  without
     additional license agreements.

************Text  has been omitted pursuant to a confidentiality  request to the
Securities  and  Exchange  Commission.  Omitted  text  has been  filed  with the
Securities and Exchange Commission.

                                                                          Page 5
<PAGE>
All of the terms and conditions of the Agreement shall remain  unchanged  except
as specified above.

SIGNED in multiple originals this the __ day of __________, 2000.

                                        ORTHOLOGIC CORP.

                                        By:
                                            ------------------------------------
                                                   Tom Trotter, President

                                        CHRYSALIS BIOTECHNOLOGY, INC.

                                        By:
                                            ------------------------------------
                                                Darrell H. Carney, President

************Text  has been omitted pursuant to a confidentiality  request to the
Securities  and  Exchange  Commission.  Omitted  text  has been  filed  with the
Securities and Exchange Commission.

                                                                          Page 6

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