PHYLUM CHORDATA 



45 1 



stage when the deposition of the eggs takes place, and it is 

 only after a more or less prolonged period of incubation that 

 the young, fully formed in almost every respect, emerge 

 from the shell and shift for themselves. Many lizards, 





Fig. 271. — Section of the pineal eye of Hatteria punctata. £-, blood-vessels ; h, 

 cavity of the eye filled with fluid; k t capsule of" connective tissue; /, lens; m> 

 molecular layer of the retina; r, retina; st, stalk of the pineal eye; .r, cells in 

 the stalk. (From Wiedersheim, after Baldwin'Spencer.) 



however, and a few snakes are viviparous, the ova being 

 developed in the interior of the oviduct, and the young 

 reaching the exterior in the completely formed condition. 



