580 



KEPTILIA 



[CH. 



4-~ 



fold (2, Fig. 284). This does not meet its fellow in the middle line, a 

 cleft existing between them. These folds conceal the eyeballs and the 

 inner openings of the Eustachian tubes which lead up to the ear- 

 drum. Palatal folds as already mentioned are found in all Reptilia. 

 Turning now to the circulatory system we find that the conus 

 arteriosus no longer exists as such, having been cleft into three 

 trunks down to its commencement in the ventricle. One of these 

 trunks is ventral and slightly posterior to the others, and gives rise 



to the two arterial arches, 

 which as pulmonary arteries 

 supply the lungs and have 

 no connection with the 

 aorta. The other two arte- 

 rial trunks form the right 

 and left roots of the aorta. 

 They cross each other at 

 their origin, that which 

 passes to the right of the 

 oesophagus arising from the 

 left of the ventricle and 

 vice versa. The third pair 

 of arterial arches, corre- 

 sponding to the carotid 

 arches of Amphibia, are 

 well developed in Lacerta 

 vivipara. They have a 

 common stem which arises 

 from the right systemic 

 arch. In some lizards the 

 longitudinal epibranchial 

 vessel of the embryo per- 

 sists between the carotid 

 and systemic arches on 

 either side, so that in this 

 respect a lizard may be 

 even more primitive than 

 a Newt, but this feature 

 seems to be confined to the 



genus Lacerta. In other Lacertilia, and indeed in all other Rep- 

 tiles, this connecting link has disappeared. 



The ventricle has projecting into its cavity two imperfect 



FIG. 287. Urine-genital organs of male Lizard. 



1. Testis. 2. Vas deferensr=archinephric 

 duct. 3. Epididymis = (mesonephros). 

 4. Kidney = metanephros. 5. Ureter. 

 6. Bladder. 7. Rectum cut and turned 

 back. 8. Cloaca laid open. 9. Open- 

 ing of vas deferens. 10. Groove leading 

 to opening of penis. 11. Penis. 12. Dor- 

 sal aorta. 



