EXERCISE VII 

 BREEDING HABITS OF VERTEBRATE ANIMALS 



A knowledge of the anatomy of the reproductive organs is essential 

 to an understanding of the breeding habits of vertebrates. In order to 

 gain this knowledge the student should work out the structure of the male 

 and female reproductive systems in the frog, using for this purpose dis- 

 sections which are placed on the table. He should also consult the charts 

 which will show the relative location of the organs and their connections. 

 Examine also a model of the frog showing organs, and specimens partly 

 dissected. 



A. ANATOMY 



1. Male Reproductive Organs. In the dissection furnished you note: 

 la. The kidneys, two flattened oval structures side by side. Near 



their anterior ends find: 



16. The testes (singular testis), two yellowish bodies of ovoid shape. 

 Push one of them aside and observe: 



Ic. The vasa efferentia (singular vas efferens), delicate white tubes 

 passing between the testis and the median edge of the kidney. 



Id. The ureters are tubes, one passing backward from the lateral 

 margin of each kidney. They connect the kidneys with: 



le. The cloaca, a short passage which is a continuation of the large 

 intestine. (The large intestine and part of the small intestine are 

 included in your specimen.) The cloaca discharges to the exterior through 

 the anal aperture. If your demonstration specimen is from the species 

 Rana pipiens, find also : 



If. The Muellerian ducts, two irregular white tubes extending from 

 the cloaca forward to a point in front of the kidneys. They correspond 

 to the oviducts of the female, but are functionless in the male. 



Make a diagram of the male reproductive system. Discover if 

 possible how the spermatozoa reach the water. 



2. Female Reproductive Organs. In the demonstration dissection 

 furnished find: 



2a. The ovaries, two large lobed masses containing black and white 

 eggs (or the ovaries may be much smaller and white). 



2b. The oviducts, two thick convoluted tubes extending longitudinally 

 beside the ovaries. 



2c. The uterus, a thin-walled portion of the posterior end of each 

 oviduct. Each uterus connects with: 



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