In other words their gut penetrates their brain. In most species, a subesophageal or buccal ganglia controls the mouth parts or feeding apparatus. Much seemingly normal behavior can occur in many forms when the circumesophageal connectives are severed, pointing to many higher level functions of the subesophageal ganglia. Segmental Ganglia - Where fusion has not occurred, the postural musculature, appendages, organs, etc. are controlled by circuitry resident in segmental ganglia. The functions of segmental ganglia vary among groups.
Serial specialization is as important as serial homology in the funtion of the ladderlike chain.
Techniques of Investigation Neuroanatomy can be investigated at many levels, including the overall gross organization of connectives, commissures and ganglia, as well as at the level of single cells. Gross Anatomy - The overall anatomy of the CNS can be examined by blunt dissection. In particular, it is important to determine the homologies between different forms with regard to the anatomical interrelations of different ganglia, the sense organs and their afferent nerves as well as the efferent systems including peripheral ganglia, motor nerves and effector organs. Microanatomy - The cellular anatomy of invertebrate ganglia can be readily examined in whole mounts, in situ, using Methylene blue staining in freshly dissected preparations. A detailed protocol for the use of Methylene blue is attached.