SPERMATOGENESIS 141 



to the middle piece (Fig. 63, G), which contains the basal granule 

 of the tail filament. It has a fairly thick cytoplasmic sheath. 

 The tail itself contains only the tail filament surrounded by a very 

 delicate cytoplasmic envelope. 



The structure of the spermatocyte is quite simple, and very 

 unlike that of the spermatozoon. The nucleus is eccentrically 

 placed, and has by its side the Golgi apparatus, which consists 

 (according more or less to the method of fixation) of a spherical 

 shell incomplete on the side apposed to the nucleus, a reticulum 

 or a number of rodlets (batonettes) arranged or enclosing a mass 

 of modified cytoplasm, the idiosome (Fig. 66, A, etc.). In the 

 centre of the idiosome are the centrioles (Fig. 66, A). There is no 

 definite connection between these two structures, although they 

 are associated in this phase. In the later spermatocyte the Golgi 

 apparatus with the idiosomal material breaks up into separate 

 Golgi bodies (= rodlet + idiosomal cytoplasm), and becomes 

 scattered throughout the cell. The mitochondria at this stage are 

 in the form of granules or filaments, and are usually evenly 

 distributed (Figs. 64, A, 65, A). 



In the spermatocyte divisions the Golgi bodies are gathered 

 into subequal groups, and accompany the centrioles as they 

 separate on the formation of the spindle (Figs. 63-64, B, C). 

 The mitochondria, however, usually lie around the spindle, and 

 are only separated into two groups by being mechanically cut in 

 two by the formation of the inter-cellular wall (Fig. 64, C). 



The resultant spermatids are very like the late spermatocytes, 

 but are, of course, much smaller (Figs. 63-66, D). Now follows 

 the process of spermatoleosis, or metamorphosis, of the spermatid 

 into the mature spermatozoon. 



The centrioles are usually at what is to be finally the anterior, 

 or " tip " end, of the spermatozoon. They are packed in between 

 the nucleus and the cell wall (Figs. 63-66, D). On the other side 

 of the nucleus there comes to be formed the acroblast. This is 

 derived from the Golgi bodies by their fusion into a spherical form 

 with the idioplasm inside (Figs. 63-66, D). In the centre of this 

 is formed the acrosome (Figs. 63-66, D). In some forms, such as 

 the mammalia, hemiptera and amphibia (Bowen), the acrosome 



