l62 



THE GERM-CELLS 



choplasm " or " kinoi^hism ") which is found in the spermatid in the 

 form of a sphere (sometimes an attraction-sphere) or " Nebenkern " 

 or both. Apart from the nuclear history, these facts have been 

 definitely determined in only a few cases, and much confusion still 

 exists in the accounts of different observers. Thus a number of 

 investigators {e.g. Platner, Field, Benda, Julin, Prenant, Niessing) 

 have asserted that the centrosome passes into the acrosome, instead of 



a 



N- 



Fig. 82. — Formation of the spermatozoon in an insect, A/iasa. [Paulmier.] 

 A. Telophase of secondary spermatocyte-division, showing extra chromosome (small dyad of 

 Fig. 127) below. B. Reconstitution of the nuclei. C. Spermatid with Nebenkern (yV) and 

 acrosome (a). D. Nebenkern double, with centrosome between the two halves. E. F. G. Elon- 

 gation of the spermatid, outgrowth of axial filament, migration of acrosome. H. Giant spermatid 

 (double size) with two centrosonies and axial filaments. /. Giant spermatid (quadruple size) 

 with four centrosomes and axial filaments. 



the middle-piece — a result which stands in contradiction with the fact 

 that during fertilization in a large number of accurately known cases 

 the centrosome arises from or in immediate relation to the middle- 

 piece (Amphibia, echinoderms, tunicates, annelids, mollusks, insects, 

 etc.; see p. 212). The clearest and most positive evidence on this 

 question, afforded by recent observations on the spermatogenesis of 

 insects, annelids, mollusks. Amphibia, and mammals, leaves, however, 

 little doubt that the former result was an error and that, as the facts 



