26o Susanjia Phelps Gage 



histological studies necessarj^ for a complete investigation have 

 not been made. 



METHODS. 



As the brain is small — 6-7 mm. long in the adult— only a 

 few general facts can be arrived at by its study as a whole. 

 The skull is extremely hard, and the removal of a fresh brain 

 is difficult, hence specimens in which bone was developed 

 were decalcified and sectioned through the entire head (17). 



The specimens were killed by chloroform or strong alcohol, 

 put immediately into picric alcohol, hardened in 67 and 82 

 per cent, alcohol, dehydrated and cut in collodion. Hsemat- 

 oxylin and a variety of carmine stains were used. The nerves 

 and larger nerve tracts are well marked, and in some series 

 the deep origin of nerves can be traced with great distinctness, 

 while the natural relation of parts to each other and to the 

 membranes is left undisturbed. 



Only young larvae needed no decalcification. A few brains 

 were removed and prepared by a modification of Golgi's 

 method. Embryos were hardened in Perenyi's fluid after re- 

 moval from the ^%% capsule. 



About 70 series of sections of the head were made. Groups 

 of three specimens agreeing as nearly as possible in size and 

 development, were cut in the three planes, transverse, sagittal 

 and frontal, in order to correct errors due to loss of substance 

 in cutting and to ensure the natural arrangement of parts in 

 drawing. 



The photographic reproductions in Plate i show the char- 

 acter of the material, the eye only, of the macroscopic parts, 

 is imperfect, the lens being so hard that its removal was nec- 

 essary. Cilia, when present, were perfectly preserved in the 

 mouth and nasal cavities, but were not found within the brain 

 cavities. Whether this is due to their absence or the re- 

 tarded penetration of the hardening agents is not known ; 

 other details of structure are clear. ^ 



HISTORY. 



The brain of diemyctylus has been little studied. Mason 

 (32) shows by a photographic process a transection through 



