HkrhK'K, .\f()rpho/oov of \crvo/is Syslc/n. ^i 



are necessary. In the embryos of the black-snake, fre- 

 quently referred to above, the fibres from the greatly elong- 

 ated olfactory lobe collect in rather small bundles and pass 

 to the Schneiderian epithelium either of the nasal cavity or 

 of Jacobson's organ. The fibres destined to the latter collect 

 from the mesal aspects of the lobes and form strong bundles 

 passing ventrad, though there is no sharp regional diff'eren- 

 tiation. The epithelium of the two organs at this stage is 

 nearly identical, but the granular sub-epithelial layer of the 

 nasal passages is nearly homogeneous, while that of Jacob- 

 son's organ has a follicular or lobose structure and receives 

 a larger proportion of nerves. 



RRAIN OF THE TITRTI.E ( ASPIDONECTES SPTNIFEr). 



The brain of the small specimen of Aspidonectes figured 

 may serve as a rather generalized type for the Chelonida". 

 In many respects the external configuration reminds one of 

 that of the lizard. The abrupt flextures described by the 

 axis and the extremely small size of the hemispheres are 

 best seen from sections. The olfactory lobes are super- 

 ficially fused ventrally and are so closely appressed upon 

 the hemisphere that they may easily be regarded as a part of 

 the latter. The real shape of each of the hemispheres is 

 a very obliquely-placed ellipsoid, bearing a more or less 

 conical protuberance cephalad. The diencephalon presents 

 no noteworty peculiarity, except the great relative size and 

 independence of the medi-commissura. The optic lobes are 

 very high and large, their median length being much greater 

 than that of cerebrum. The ventricles of the mesencephalon 

 are large and extend far laterad, while the tectum is highly 

 developed. 



Histology. — In the turtle the distinctions between the 

 areas of pyramidal and fusiform cortical cells are quite ob- 

 vious. The whole lateral surface is covered by a thin layer 

 of the pyramidal cells with deeply staining nuclei. In the 

 perpendicular section (Fig. 2, Plate III) through the lateral 



