410 



COLLEGE ZOOLOGY 



malian diaphragm: to enlarge the coelom 

 and cause air to be "sucked" into the lungs. 

 To accomplish expiration, the turtle uses 

 paired expiratory muscles which enclose the 

 viscera. Air is forced out of the lungs by the 

 contraction of the expiratory muscles which 

 press the viscera against the lungs. This ac- 

 tion is assisted by pulling in the legs and 

 neck, which further decreases the size of the 

 body cavity. 



Many aquatic turtles probably carry on 

 respiration to some extent by taking water 

 into the cloaca and the accessor}' bladders 

 and then forcing it out through the cloacal 

 opening. Thus these structures may serve 

 as supplementary respiratory organs (com- 

 pare with sea cucumber, and nymph of 

 dragonfly). It has also been sugested that in 

 the aquatic forms certain areas of the skin 

 may be modified for respiration. 



Urogenital system 



Excretion is carried on by the two kid- 



neys. Their secretions pass through the 

 ureters into the cloaca (Fig. 277), are stored 

 in the urinary bladder, and then make their 

 exit through the clccal opening. This is 

 often called the anr?, but the anus properly 

 refers to the open'^g of the digestive tract; 

 therefore, in those forms with a cloaca, this 

 term should apply to the opening of the 

 intestine into the cloaca. 



The sexes are separate. The male organs 

 are a pair of testes and a pair of vasa 

 deferentia through which the sperms pass to 

 the grooved copulatory organ or erectile 

 penis attached to the ventral wall of the 

 cloaca. It should be noted that the reptiles 

 are the first vertebrates in which there is a 

 penis. The female organs are a pair of 

 ovaries and a pair of oviducts; the latter 

 open into the cloaca. The sperms are in- 

 jected into the female by a sexual act 

 (copulation), usually preceded by courtship 

 behavior. 



Turtles are oviparous. The eggs which are 

 white, round or oval, and covered by a more 



Testis 



Kidney 



Rectum 



Urinary bladder 

 Vas deferens 



Penis 



■Ureter 



Bladder opening 



Accessory bladder 



Penis groove 

 Cloaca 



Figure 277. Cloaca and urogenital organs of a turtle, ventral view. (After Gegenbaur.) 



