Herrick, Brain of Certain Rcpti/cs. 103 



of cither side. Laterad of this ceU ^roup is the tract from the 

 supracommissure, which is a strong bundle entering the cere- 

 brum at the point where the peduncles cross. Farther caudad 

 the habena appears and niduli develop in the path of the dorsal 

 peduncles. 



One of the most remarkable peculiarities of the turtles is 

 the development within the infra-habenaria of a very large spher- 

 ical nidulus with a densely cellular core and radially arranged 

 peripheral band and a concentric cellular envelope. Its struc- 

 ture is closely analogous to that of the ruber of fishes but is a 

 specially differentiated portion of the infra-habenaria. 



The infundibular region is so much produced ventrally in 

 turtles that one is easily deceived as to the relative position of 

 the parts and this structure might be located far dorsad if we did 

 not obsesve that it is flanked by the small geniculata, and bor- 

 dered ventrad by the nidulus subthalamicus. 



In sections farther caudad the habena is shown to be 

 sharply limited from the thalamus. The sensory peduncles 

 break up in connection vyith the above concentric nidulus ("cen- 

 tral nucleus of thalamus" of authors, or "nidulus centralis.") 

 The other parts of the infra-habenaria, subthalamicus and gen- 

 iculata also receive scattered tracts, but part of the fibres pass 

 to a dense cluster at the cephalic boundary of the mesen- 

 cephalon, which we identify with the ruber. 



The motor peduncles pass on to the pes-pedunculi and in 

 the "crusta" form associations with the mid-peduncle of the 

 cerebellum. The infundibulum is not only greatly produced 

 ventrad but its tip is flexed backward much as in the amphi- 

 bia. At the apex is a paired diverticle analogous to the re- 

 cessi infundibuli or mammillaria of fishes. 



For material used in this instalment our oliligations are to 

 Professor Charlton, of Denton, Texas, whose kindness in re- 

 peatedly sending collections of Phiynosonia coronata we grate- 

 fully acknowledge, to Reverend C. L. Seasholes, who has sup- 

 plied similar specimens, to Mr. George Osbun, who collected a 

 variety of lizards in Alabama, the study of which is not yet 

 begun, to many other friends who have assisted in similar ways. 



