14 CAPT. 0. F. U. MEEK ON THE 



massing at the poles ; on these occasions it appears in the form of two Vs, 

 whose apices are distally placed with respect to one another. An illustration 

 of this phenomenon is given on Plate 3. fig. 28. This " lagging '" of the 

 heterotropic chromosome has been observed by Baumgartner in Gryllus, by 

 Davis in numerous members of the Acrididse and Locustidse, and by many 

 writers in the case of other types. 



The cytoplasm becomes constricted shortly after the chromosomes have 

 passed to the two poles, and in this manner two daughter spermatids are 

 formed. 



Spermatids. 



As soon as the nuclear membrane of the spermatids has formed, the 

 chromosomes become ragged, and dissociation of their component granules 

 begins to take place. This process continues until the individuality of the 

 ordinary chromosomes is completely lost, the nucleus exhibiting several 

 irregularly placed blotches, in which the chromatin granules are faintly 

 distinguishable. The heterotropic chromosome retains its individuality for 

 a considerable time, remaining intact as a darkly stained body in the midst 

 of the dissociating ordinary chromosomes ; it subsequently becomes resolved 

 into a mass of granules, and loses its identity in the general chromatin 

 reticulum. Plate 3. fig. 29 shows a cell at this stage of development. 



Shortly after this a body appears outside and in contact with the nuclear 

 membrane, forming a conspicuous object on account of its great affinity for 

 the iron hsematoxylin and its characteristic bead or knob shape. The axial 

 filament grows out from a clearly marked constriction in the middle of this 

 " centrosome,'' and, as the cytoplasm of this region gradually elongates to 

 form the tailpiece of the unripe spermatozoon, increases in length and 

 appears as an indistinct line down its entire length. The chromatin granules 

 have now become extremely minute, and the nucleus has the appearance 

 of an uniformly grey body, in which the component chromatin particles 

 cannot be distinguished. This gradual transformation is shown on Plate 3. 

 figs. 30 & 31. 



The elongation of the tail and axial filament is later accompanied by a 

 corresponding elongation of the nucleus, which loses its spherical shape and 

 appears in that of a torpedo. The " centrosome " still occupies its original 

 position between the axial filament and the posterior end of the nucleus, but 

 is slightly reduced in size ; this can be clearly seen in figs. 32 & 33. 

 The lengthening of the nucleus and tailpiece continues, and the "centro- 

 some " becomes smaller and smaller. The nucleus gradually becomes darker, 

 doubtless owing to a closer association of its chromatin particles. Plate 3. 

 figs. 34 & 35 show this further elongation, the reduced size of the 

 " centrosome " being very noticeable, 



