ANATOMY OF THE TURTLE. 



509 



mesentery, and contains three oval eggs, one of which is 

 lettered Eg. The oviduct can be followed to its anterior 

 end which is much pigmented and has a terminal opening. 

 The cut-end of the left oviduct (ovd) shows the folds of the 

 lining mucous membrane. 



The ovary (o) is likewise suspended by a thin membrane, 

 the mesovarium, and is equally developed on both sides in a 

 complete specimen. It is easily recognized by the numerous 

 bulging yellow spheres, of all sizes, which are the egg-yolks 

 in various stages of development. 



The heart of the turtle (Fig. 447) will repay careful dis- 

 section. A small round body lies just in front of it ; this is 

 usually considered the equivalent of the thyroid gland, 

 through its real nature is still un- 

 certain. The heart itself (Fig. 447) 

 consists of two auricles and one 

 ventricle (ven), with an imper- 

 fect internal septum. It receives 

 the veins upon its dorsal surface, 

 and gives off the arterial trunks 

 from its ventral side. The two 

 auricles are equal in size ; together 

 they a little more than equal the 

 ventricle. The arterial vessels arise 

 together a little to the right, and 

 are most conveniently described as 

 three in number : 1st. The right 

 aorta (R Ao} arising on the left ; 

 2d. The left aorta on the right 

 (L Ao) ; the two cross near their 

 origin and curve upwards and back- 

 wards, to reunite posteriorly just in front of the retractor 

 muscles, their union forming the single median descending 

 aorta; 3d. The pulmonary aorta (pa), which soon divides 

 into a branch for each lung. The left aorta gives off a 

 branch (d) which persists as a mere cord, the remnant of the 

 dudus arteriosus, which originally united the aorta with the 

 pulmonary artery. The right aorta gives off an innominate 

 branch, that soon divides, and from each division springs 



Fig. 447. Ventral surface of 

 the heart of the Turtle, Chryse- 

 mys plctn. Dissected and drawn 

 by C. S. Minot. 



