494 ZOOLOG T. 



'bellu m is small, especially in the serpents. In the croco- 

 diles the brain most approaches that of birds, the cerebellum 

 being larger than usual in the middle, and in this respect 

 somewhat approaching the birds. Corpora striata (which 

 are thickenings of the outer walls of the cerebral hemispheres) 

 and the anterior commissure of the cerebral hemispheres are 

 present for the first time in the vertebrate series. 



The kidneys (Fig. 440, k) are tabulated, varying in foim. 

 and position, and usually situated near the cloaca, the ureters 

 being short and opening into the cloaca. The reproductive 

 organs are generally like those of the Batrachians. The 

 ovaries lie on each side of the vertebral column, and vary in 

 size with the season, being largest during the time of repro- 

 duction. The oviducts (Fig. 440, n) are voluminous coiled 

 canals, which in most reptiles open into the cloaca ; in the 

 turtles, however, opening into the neck of the so-called 

 urinary bladder. After the egg passes into the oviduct it 

 is enveloped by the "white" or albumen, which is secreted 

 in the anterior part of the oviduct, while the thick-walled 

 terminal part secretes the shell. 



The external differences between the sexes is more marked 

 than in the Amphibians. According to Darwin, the sexes of 

 the Chelonians and snakes differ very slightly ; male rattle- 

 snakes are said to be more yellow ; in the East Indian Dip- 

 sas ci/nodon the mule is bright green, while the female is 

 bronze-colored. Male lizards are usually larger, while male 

 snakes are always smaller than those of the opposite sex. 

 Various appendages, suoh as crests, warts, horns, etc., when 

 present in both sexes, are most developed in the males, 

 while the colors and markings are brighter in the latter sex. 



The moulting of the skin is effected by its being pushed off 

 l>y the upward growth of fine, temporary cuticular hairs. 

 On certain parts of the body, as on the underside of the 

 capsular skin and scales of the eyes, these hairs do not de- 

 velop. After the skin is loosened, it dries and is readily 

 shuffled off. 



The eggs of turtles, like those of birds, are very large, 

 the yolk mass being greatly developed. The lizards, snakes, 

 and crocodiles lay their eggs in sand or light soil, while those 



