Herrick, Brain of Certain Reptiles. 93 



physis is slung by its membranes in such a way that it is at- 

 tached ventrad to the region of the supracommisure and dorsad 

 to the cranium. Even at the earHest stage observed it has the 

 adult characters and is accompanied by a special blood vessel. 

 The spaces occupied by the sinuses are subsequently encroached 

 on by the hemispherses and the epiphysis comes to lie between 

 the former. 



The histological structure of the globular part of the epiphy- 

 sis is peculiar. At first glance it seems to be a solid mass of deep- 

 ly stained corpuscles, but inspection proves that it is formed of a 

 ramosely branched tube which is closely packed within the 

 space alloted to it. Each branch is enveloped by a delicate 

 sheath of connective tissue and the interspaces in some species 

 contain blood vessels and pigment while in others they are 

 almost devoid of foreign elements. A large vessel lies caudad 

 of the organ and follows its course. There are no paraphyses 

 of sufficient prominence to be confused with the epiphysis. Its 

 structure suggests a lymphoid gland and its size indicates that it 

 is not entirely functionless. When it shall be recognized that 

 nutritive processes are closely associated with all sensory organs 

 it will cease to surprise us that a rudimentary sensory structure 

 should function as a nutritive apparatus. 



The epiphysis in turtles is one of the most instructive in- 

 stances of an intermediate link. It develops, as in birds, in the 

 form of a diverticle from the diencephalic roof immediately 

 caudad of the supracommissure and increases rapidly in size. In 

 the larger turtles it becomes a relatively enormous lobate sac con- 

 nected by a tortuous tubular stalk with its origin. The perfora- 

 tion never fully closes but is so small as to be easily overlooked. 

 The peripheral part becomes irregularly lobed and enveloped by a 

 close net-work of blood vessels and connective tissue so that its 

 lumen is partly encroached upon. Nevertheless it retains a close 

 resemblance to the same organ in Phrynosoma, while far on its 

 way toward the extreme modification afforded by Ophidia. The 

 parietal organ and nerve have not been detected, though the 

 resemblance is so close to the saurians in which they are devel- 

 oped that it would not be surprising if they should yet be found 



