662 



BASHFORD DEAN, 



into the body cavity through a loop-shaped Perforation, the foremost 

 (morphologically) pronephric fuunel; a second opening is iramediately 

 behind (actually anterior to) it; and traces of a third immediately 

 behind the second. By this is meant that the pronephric duct 

 establishes temporarily a third connection with the coelomic wall, 

 although the writer could not discover that a Perforation subsequently 

 occurred. This trace, however, seems noteworthy in view of the 

 greater number of pronephric tubules of Lepidosteus and Äcipenser. 

 On the other band the reduced number of the pronephric tubules is 

 certainly of interest as a condition transitional to that of the Teleost, 



e) Brain, neuromeres, hypophysis. 

 In the account of the early development the brain and spinal 

 cord have been shown to have had their origin in a solid ectodermic 

 thickening. In a late embryo, slightly earlier than that of PL 9, Fig. 1, 



L o 



RO 



Figs. N— Q. Sagittal sccfions of brain of embryonic and larval Amia. Fig. R. 



Sagittal section of brain of Salmo fario at batcliing. Fig. N of embryo surrounding 

 about 195" of egg's circumferenee. Fig. O of lurva at hatching. Fig. P of larva four 

 days old. Fig. Q of larva four weeks old. cerebellum, CA anterior commissure, CH 

 chiasma, CH' iiotochord, CP po.sterior commissure, CS superior commissure, DE commis- 

 sura debilis, E epencephalon (Kupffeu), /i'Pepiphysis, i«" forebraiu, tG foregut, // liind- 

 brain, UY hypophysis, / inlundibulum, LO lobus olfactorius impar, M midbraiu, M' 



