i3 6 
MAMMALIAN ANATOMY 
( d ) Spermatids, formed by the division of the secondary 
spermatocytes; they are half the size of the latter and twice as 
numerous, and lie almost or quite detached in the lumen of the 
tubule until they begin to elongate and reach in clusters between 
the columns of spermatogonia and spermatocytes in the wall of the 
tubule, and attach themselves to certain large pyramidal nutritive 
cells which lie on the basement membrane and are known as 
the Sertoli cells. These support and nourish the spermatids 
during their transformation into spermatozoa. 
(e) Spermatozoa, the fully developed male germ cells; these are 
greatly elongated, motile cells with lance-shaped heads (in the rat) 
in which the nucleus is located, and a long filamentous tail which 
serves as the organ of locomotion, by means of which the cells 
move freely in the tubules and the ducts. (Cf. living spermatozoa 
of rat, guinea pig, or some amphibian, and demonstration slides 
showing human or other spermatozoa.) 
Draw details of various tubules to show as many as possible of the 
stages in the growth and development of the male germ cells. 
