206 AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



the glomerulus, formed by the. breaking up of a branch of one of 

 the renal arteries. The capsule and glomerulus together are 

 known as a Malpkigian body. A convoluted tubule in which four 

 regions can be distinguished succeeds Bowman's capsule. These 

 regions are (1) a short neck, lined with ciliated epithelium; (2) a 

 much convoluted glandular, part, lined by columnar epithelium 

 which is pigmented and granular ; (3) a second ciliated section ; 

 and (4) a collecting portion. 



The urinary dud is formed by the union of the collecting 

 portions, and is at first imbedded in the kidney on its outer side. 

 The renal-portal vein breaks up into capillaries which closely 

 surround the glandular parts of the uriniferous tubules, and are 

 joined by the small veins coming off from the glomeruli. 



The nitrogenous waste of the body (as urea, CH 4 N 9 0), together 

 with much water and various salts, is excreted by the kidneys. 

 The water and salts are filtered from the glomeruli into Bowman's 

 capsules, while the urea is excreted by the glandular parts of 

 the kidney-tubules. The urinary bladder serves as a temporary 

 receptacle for the urine. 



Male Reproductive Organs (Fig. 51). An oval, yellowish, 

 spermary (testis), enveloped in pleuro-peritoneum, is closely con- 

 nected by a double fold of the same, the mesorchium, with the 

 inner side of each kidney. In this fold a number of delicate 

 tubules, the vasa efferentia, run from one organ to the other. The 

 two spermaries are commonly unequal in size. In It. esculenta 

 the urinogenital duct is considerably dilated just as it leaves the 

 kidney, and in R. temporaria an oval glandular mass, the vesicula 

 seminalis, is placed on its outer side immediately before it enters 

 the cloaca. 



The male Frog is distinguished externally by the characters 

 mentioned on pp. 175 and 176. 



The spermary is essentially composed of seminiferous tubules, 

 lined by epithelium, and opening into a central cavity. From 

 this the vasa efferentia arise, and, after traversing the mesorchium, 

 enter a longitudinal canal imbedded in the inner edge of the 

 kidney, and giving off numerous transverse tubules, which join 

 the collecting parts of the uriniferous tubules just before they 

 enter the urinary duct.. The sperms (spermatozoa) are thread- 

 like bodies, with narrow cylindrical heads and vibratile tails. 

 They are developed from spindle-shaped sperm -mother -cells, 



