Some pointB in the Spermatogenesis of Mammalia. 153 



mammalian spermatogenesis , without in tlie least affecting the here- 

 ditary qualification of the resulting elem^etits. 



At or about the period we have been discussing, the nuclei ol 

 the spermatids in the rat show an ever increasing tendency to become 

 pointed, always on that side of the cell which looks towards the 

 lumen of the tubule (Figs. 15, 20). This little point becomes quite 

 sharp, and an excessively small body (cc) is, eventually, apparently 

 extruded through the nuclear membrane; it is of not more than the 

 fifty- to the sixty-thousandth of an inch in diameter, it has an extre- 

 mely sharp contcfiir and stains apparently like the intranuclear mikro- 

 somes. Concomitantly with its appearance, there is seen, stretching 

 away from the little body across the cytoplasm of the cell and always 

 in the direction of the lumen of the tubule, an excessively faint band, 

 which later projects beyond the circumference of the cell and forms 

 tlie embryonic tail of the spermatozoon. 



Fairly concurrently with these appearances during the formation 

 of the tail, and often a little before them, the archoplasm entere upon 

 an extraordinary metamorphosis, which has been briefly described by 

 Benda, in the paper to which I have referred. The exact period at 

 which this change occurs is by no means constant, but it always comes 

 on when the existing crops of spermatozoa have assumed theii' cha- 

 racteristically elongated form, and when their still adherent residual 

 corpuscles project, together with their tails, into the lumen of the tubule. 



At this period, the spermatids are more or less rounded bodies, 

 crushed into the narrow spaces between the columns of spermatozoa. 

 The archoplasm of these elements is a more or less triangular well- 

 marked body, with its broad base tending to sit cap-wise on the sur- 

 face of the nucleus. Up to the time in question it presents (even 

 when viewed with the highest powers) nothing but a finely fibrous or 

 granular texture; but suddenly (and almost, though not quite, simul- 

 taneously in every cell) the archoplasm Fig. 17 a is seen to become 

 filled with minute clear globules. At first they appear numerous, often 

 reaching a total of thirty or forty, and extremely small; as time goes 

 on, however, they are seen to be rapidly increasing in size and di- 

 minishing in number. In other words, theii' growth is caused h g a 



