THE MALE GENITAL TRACT. 815 



only. My own observations prove that the radiating rows of 

 epithelia coalesce into continuous masses, in the most peripheral 

 portions of which the heads of the spermatozoids are produced, 

 while the tails are formed by the more central parts. 



The steps in the formation of spermatozoids are as follows : 

 The epithelia nearest the connective tissue become coarsely 

 granular, and in part nucleated j next we see enlarged epithelia, 

 in which the bioplasson assumes irregular, rod-like forms, 

 arranged without much regularity. Then follows a layer com- 

 posed of coalesced epithelia, the bioplasson of which has grown 

 into bulky formations, which are the heads of the spermatozoids r 

 while the rods in the central portions of the rows become paral- 

 lel, and coalesce to form the tails. Around the spermatozoids 

 numbers of unchanged bioplasson-granules are seen, and the 



FIG. 370. TESTIS OF A EAT. 



G, connective-tissue slieath, producing septa between the seminiferous tubules, in wliicn 1 

 course the blooil- vessels F ; E, rows of epithelia of the seminiferous tubules ; 8, tails of sper- 

 matozoids, filling the caliber of the tubule. Magnified 200 diameters. 



first-formed spermatozoids are studded with these granules. As 

 the liquefaction of the unchanged bioplasson i. e., the forma- 

 tion of mucus proceeds, the tails appear smooth and without 

 any attached granules. Coarsely granular plastids, in limited 

 numbers, are left unchanged, and mixed with the completed 

 sperm. (See Fig. 371.) 



The epithelia of the straight seminiferous tubules are col- 

 umnar; those of the plexus, within the corpus Highmori, are 

 flat. Neither of these take any part in the formation of sper- 

 matozoids. 



