g6 Laboratory Guide in Zoology 



X. — If the specimen is a male, two small, oblong, light- 



colored bodies, the testes, will be found, one on each 

 side of the median line just anterior to the cloaca. 

 They produce sperm cells that pass directly by minute 

 tubes into the kidney and thence by the ureter to the 

 cloaca and to the exterior, where they fertilize the eggs 

 from the female. 



XI. — Excretory Organs. Excretory organs are used to 

 throw off the waste material of the body. Hence the 

 lungs, kidneys, and skin may be grouped together as 

 parts of the excretory system. We have here only to 

 study the kidneys. These are two flat, oblong bodies, 

 lying one on each side of the median Une in front of 

 the cloaca and dorsal to the testes. As the blood passes 

 through the walls of these bodies, it is relieved of certain 

 waste materials that pass through ducts, the ureters, into 

 the cloaca by openings in its dorsal wall. The bladder 

 is a colorless bag which opens into the ventral side 

 of the cloaca. Find the ureters. 



XII. — Skeleton. Cut away the viscera already studied, 

 leaving the backbone, or spinal column, exposed on its 

 ventral side. Cut away the muscles on the fore and 

 hind legs without severing the ligaments that bind the 

 bones. Notice that in its general plan the skeleton 

 is made up of a central axis (spinal column) and its 

 appendages (limbs, etc.). Notice the segmented char- 

 acter of the backbone. Each segment is a vertebra. 

 The unsegmented posterior part of the axis represents 

 the fused segments that form the tail in other verte- 

 brates. 



XIIL — Nervous System. This may be divided into two 

 great divisions, — the cerebrospinal and the sympathetic. 

 The cerebrospinal system is made up of the brain and 



