466 



DERSHEiM, I find the same marked simplicity of form and structure 

 which characterizes the Polypterus as described by Waldschmidt ^). 

 It will be seen from the following description that the indications of 

 a primitive character are even more distinct than in case of the 

 Polypterus. The hypophysis of the Calamoichthys is an elongated, 

 rounded structure which extends backwards from the infundibulum for 

 a short distance, passing parallel to the ventral surface of the brain 

 and resting in a special cavity, the walls of which separate it from 

 the brain and mouth region. It may be said to consist of two parts, 

 a nervous or infundibular portion, and a glandular portion or hypo- 

 physis proper. 



The first portion corresponds to that part in other forms designa- 

 ted as the "nervous portion" by Edinger*) and Burckhardt ^), but 

 differs much from the same in the forms described by them being 

 much simpler in structure: here there is no folding of the walls of 

 the infundibular part, to form a saccus vasculosus or lobi, and no 

 appearance of a glandular structure in connection with the nervous 

 tissue. It consists simply of a very short tube-like prolongation of 

 the ventral wall which passes directly over into the glandular part, or 

 hypophysis proper with which it appears to be intimately connected, 

 there being no distinct line of demarcation between the two tissues. 

 The nervous structure is fully retained up to this point of union. 

 This intimate connection of the two parts represents the other extreme 

 from the conditions as found in many other forms, for example in 

 the Forelle, as described by Rabl-Rückhard ^), where the saccus 

 vasculosus-portion and hypophysis proper are completely separated. 

 In fact in all forms where the conditions are more complex, the se- 

 paration of these two parts appears to be more or less complete. 



The hypophysis proper, or glandular part, extends backwards from 

 the nervous portion as a thickwalled tube which becomes smaller as 

 it approaches the end. The cavity of the third ventricle is prolonged 

 nearly throughout the whole hypophysis; at first triangular in form 

 (see Fig. 1) it becomes more rounded and flattened as it approaches 



1) Beitrag zur Anatomie des Centralnerven systems und Geruchsorgans 

 von Polypterus bichir, Waldschmibt. Anatom. Anz., 2. Jahrg, 1887. 



2) BuBCKHARDT, Das Ceutralnervensystera von Protopterus annectens. 

 Berlin 1892. 



3) Edinger, Untersuchungen über die vergleichende Anatomie des 

 Gehirns, 1893. 



4) Eabl-Rückhaed, Das Großhirn der Knochenfische und seine Anhangs- 

 gebilde. Arch, für Anat, und Phys., 1883. 



