EXCRETORY AND REPRODUCTIVE SYSTEMS 207 



and excretory products. In the above features the Mono- 

 tremes resemble the Amphibia and reptiles. All mammals are 

 viviparous except the Monotremata, which are oviparous, lay- 

 ing eggs as large as those of the robin. The Ornithorhynchus 

 incubates its eggs in an underground nest, while the Echidna 

 carries her single egg in a temporary abdominal pouch. 



The Marsupialia bring forth their young in a very immature 

 condition. They are then carried for several months in an 

 abdominal integumentary pouch, the marsupium, within which 

 are the nipples. In the Monotremata, Cetacea, Sirenia, and 

 elephant the testes do not descend into a scrotum, but are 

 retained in the primitive location within the abdomen. In 

 Primates and some Edentates, the uterus is merely a pear- 

 shaped body without any cornua, the uterine tubes leading 

 directly into the body of the uterus. 



In the ox, bears, seals, and cetaceans the kidneys are dis- 

 tinctly lobulated. Internal evidence of lobulation is presented 

 in most mammals by the renal papillae. In the embryo, the 

 kidneys of all mammals are lobulated. 



LABORATORY STUDIES AND SUGGESTIONS 



1. What other waste products besides CO2 result from the chemical action 

 in the tissues of the body? 



2. Write a description of all parts of the urinary system visible in your 

 dissection. 



3. Bisect a kidney longitudinally in the horizontal plane, draw the cut 

 surface, and label all features. 



4. Explain the parts of a renal tubule. 



5. Wherein does the male urinary system differ from the female? 



6. Make a drawing of the uterine tubes and uterus and label all parts. 



7. Describe location, size, external appearance, etc., of the ovary as seen in 

 your specimen. 



8. How are the female reproductive organs held in place? 



9. Can you distinguish externally the termination of the uterus and the begin- 

 ning of the vagina? 



10. Are there any eggs protruding from the ovary or any cavities from which 

 eggs have been recently discharged? 



11. Describe a Graafian (vesicular) follicle. 



12. What must be added to the ovum to produce another animal? 



