New-York tribune., 1874-08-18
SIGNIFICANCE OF CLASSES AMONG THE
VERTEBRATES.
BY THEODORE GILL

The term class is that which was given
nv Ipnmus TO the most comprehensive groups of the
animal Kingdom he having Recognized no branches
or "sub-k gdoms,' modern naturahsts 90. Ine
groups OF animals subsequently combined as verte-
brates endowed with this rank were called mammals,
birds reptiles aud fishes. Concerning two OF those
classes (nammals and blrdS) no differences O! opinion
have existed since the time of LnnGus, but VII regard
all the others there is great discrepancy OF ophou
Now I'm the estimation OF the vaue OF any group onr
method is 10 take eXempars those that are ui
versally recognized as Homogeneous ana Wen es,ap
lshed The classes of mammals and birds being such,
we have then inquire what otner groups best cor
those types No groups Of animals should be comDned
in elasses which more widely dlerehtiaen @
logically each Otner than are TIC DiIu du ~
tiles, aud certainly not more than are the Dlrus anu
mammals. The thorough study OF the structure, OF
these representatives of those classes demonstrates tha
the range variation Is such that the huholoslGs
tbrou bOt each series are only general but SPECIAL
and little disguised ana that hOmOl0SOus parts are with
cacI class IT. now this criterion is applied to that
group OF old generally known the class Of fishes 1t
found fail utterly ANA the GIIcIcHCts Dc1Wccu o
extremes of that group are mmeasuraDy greater than
are those between the mammals and bIrds. and sun
still more than those between the birds ana reptiles
The betweeD such extremes and contiguous series
are also greater aud il desire TO be consistent aud 10
have taXOpOmic terms at al slehlucdn we are ptr
force compelled to assign TO such tNienes az Gai c
eutated classes within the ola group OF h'Aes ahu ~
stead OF the Old classes OF mammals, bfdS anu
fishes We have eight combined in entirely different
manner. VIZ: ~ Mammals. w piTdS' tI rcpllics' tJ
batrachians, 90 hShes V) ~ inn &
The first the last that they should be combined
in one subbTancn with WHICH the lcpJcardians should
he cOntrasted III another.
IT, now again, We proceed TO comparison and con
rast Of those classes with each other the dHereces
loom out and more distinctly. Instead OF Delns
able identify without difficulty the hom0og0ns par
in contiguous classes, becomes extremely d1cut 10
determine the general hOmoOgies OF regions ana
the numerous errors made by comparative anatomsts
before recourse mad 10 cmoFyOiocy Is suhcent
evidence Of the truth Of this statement H. Tor eX
ample we compare Amphi0rtS the only known repre-
sentative of the class OF eptOcardaus VITA IT'S nearest
related forms he marsipObIanchateS) instead OF being
able 10 find TespOndence between the several
elements OF the parts In the two types. we are
able with difficulty TO identity the beginnings OF part.
IN AmphiOruS with fuliy developed and complicated
parts in arsipObrauchiates the more profoundly our
irvcst cations pushed in all par-LcrNOus system
skeleton bronchial apparatus, vascular sNseu-the
more evident becomes the WIDE gap between the Ie-
spectivc groups Indeed, AmphOruS IN almost all IT'S
characters forms exception TO the yerteoraes ana
doubtless HFckel justified IN sOatlng AmphiOras
from all the vcrtebratc-, and II should the author
conteuded, be regarded the representative OF a
distinct sub5raEcu OF the Nerebrdtc-, all the Otncr
vcrtebrates being OppOsahie il another sub-OraucA.
There wa no discussion Prof CLIPS paper, and the
oiut paper of Profs. c. H. Hitchcock and VIM. r. Blake
was taken up. Their subject was Geological Map Of
the United States and Territories" and il was read by
Prof Hitchcock with critical and explanatory dcscrip
tlOIs.