554 BIOLOGY. 



transitional stages traversed by the animal classes during 

 embryonic development, has since then been raised to a 

 state of certainty.) 



3364. The mixture of the blood takes place through 

 an opening in the septum separating the two cardiac 

 ventricles, and which corresponds to the foramen ovale 

 of the foetus. The heart of Reptiles is therefore a per- 

 sistent fcetal heart. 



3365. Without doubt, however, the arterial blood 

 only enters the left heart, while the venous remains in 

 the right, to be thence driven into the lungs. 



3366. In other respects the foramen ovale is not a 

 true opening, but a bifurcation of the vena cava, one 

 branch of which passes into the right, the other into the 

 left ventricle, as I have demonstrated in the ' Beytragen 

 zur Anatomie' (Frankfurt bei Wesche), in treating of 

 the calf's heart. 



3367. There are generally no foramina in the body, 

 but only fissures without orifices. 



Abdomen. 



3868. The digestive organs are pretty similar to those 

 in Pishes, as is exemplified by the intestine, liver, and 

 spleen ; the digestive process is, however, more energetic, 

 and frequently aided by venom or poison. 



3369. The sexual parts are perfect. The first true 

 testes and ovaria have originated. The tegumental for- 

 mation has consequently passed over at the extremities 

 into a glandular, because the vascular system prepon- 

 derates. Even in the highest Fishes, such as the Rays and 

 Sharks, the testes and ovaria are still not developed to the 

 extent which they are in Reptiles. 



3370. In the female the oviducts pass together as 

 complete cornua into an uterus. In the male the seminal 

 ducts are still indeed separate, yet the two bodies or 

 crura of the penis are frequently developed, and continue 

 separate in the Serpents and Lizards, but are connate in 

 the Tortoises. 



3371. The kidneys are distinct and symmetrical \ their 



