Humphrey, Brain of the Snapping Turtle. 89 



point in man and anthropoid apes, and Mrs. Gage (30) finds a 

 similar opening in Diemyctylus. No metapore exists in the late 

 embryo or adult turtle. 



Endolymphatic Sacs. — The structure of these sacs differs 

 little from that shown by Norris (56) and Mrs. Gage (30) in the 

 Urodeles. The main body of these sacs lies along the skull 

 dorsad of the metencephal (Fig. 19). They send branches along 

 the caudal aspect of the gemina. These branches extend only 

 along the caudal aspect of the mesencephal not reaching to the 

 dorsal aspect as shown by Mrs. Gage in the brain of Diemyctylus. 

 A tube leads from the main sacs cephalo-ventrad along the lat- 

 ero-ventral margin of the cerebellum to the ear cavity. The pe- 

 culiar relation of this, tube to the cerebellum in the embryo is 

 shown in Fig. 18. These sacs do not unite across the meson, 

 but in some portions as shown in Fig. 19 they are separated 

 only by a blood vessel. 



Blood Sinuses of Metencephal. — Lying dorsad of the tubes 

 of the endolymphatic sacs, along the caudal portion of the 

 cerebellum, is a small blood vessel. Following it caudad we 

 soon find it widening, extending along the lateral wall of the 

 skull cavity ectad and ventrad of the endolymphatic sacs, form- 

 ing a broad sinus whose ental walls seem to be formed of the 

 dura that splits into two laminae for this purpose. Along the 

 median dorsal wall of the skull is found another large blood 

 vessel circular in transection which forms a partition between 

 the endolymphatic sacs. Tracing the sinuses caudad we find 

 them uniting across the dorsal median line forming a single ves- 

 sel which extends caudad along the dorsal wall into the neck, 

 where it grows smaller and disappears as a small blood vessel. 

 The close relation of these sinuses and the endolymphatic sacs 

 denotes a functional dependence of the latter upon a large blood 

 supply. 



Epencephal. 



The Cerebellum. — The internal structure of the cerebellum 

 is almost as simple as its outward form. It is entirely uncon- 

 voluted and has a curved outline in sagittal sections (Fig. 3). 



