REPTILES. 303 



connects by means of the fourth aortic arch of the right side 

 with the right radix aortae, and also, by both of the third arches, 

 with the carotids. This insures the supply of arterial blood to- 

 the brain, while a part of the same is carried to the dorsal aorta,, 

 which consequently contains both venous and arterial blood. 

 In Laccrta and a few other forms the third arch of either side 

 remains in connection with the radices aortae, but in all other 

 groups this connection is lost. 



Among other peculiarities of the circulation are the per- 

 sistence of a ductus Botalli (p. 187) in some chelonians and 

 crocodilia, and the varying position of the origin of the sub- 

 clavians, which may arise either from the third (carotid arch) 

 of either side, or from the right radix aortae. Subclavians are 

 lacking in the ophidia. A renal portal system occurs in all 

 except the chelonia, and in chelonia there are two hypogastric 

 veins ; in lacertilia and ophidia but one. In the latter group 

 the ^ypogastric breaks up into a plexus connected with the 'fat 

 body ; ' passing thence to the portal vein. 



The permanent kidneys of the adult reptile are the meta- 

 nephridia ; they are usually small, compact, or tabulated, but in 

 snakes the tabulation may be carried so far that the lobes are 

 connected only by the ureter. In lizards the metariephridia of 

 the two sides are sometimes united behind. The mesonephros. 

 and the \Yolffian duct are more or less degenerate, never func- 

 tioning in the adult. Their remains are more evident in the 

 female than in the male, the mesonephros forming the so-called 

 'golden yellow r body.' A urinary (allantoic) bladder is con- 

 nected with the cloaca in turtles and lizards, but in other rep- 

 tiles it is lacking. 



The gonads vary in shape with the shape of the body, being 

 broad in the chelonia, long in others. In many forms, and this 

 is especially true of the ophidia, the right gonad is larger and 

 in advance of the left. The ovaries are penetrated with a vas- 

 cular network of connective tissue. The oviducts are long,, 

 folded or contorted, and have smooth margined ostia. The ducts 

 themselves are muscular and glandular, the glandular portion 

 secreting the shell. 



Accessory reproductive organs of two types occur. In liz- 



