SPEKMATOGENESIS OF STENOBOTHRUS VIEIDULUS. 17 



the axial filament, arising near the constriction in the middle of this body. 

 The cytoplasm in this region elongates to form the tail of the unripe sperma- 

 tozoon, and the axial filament appears as a faint line running down the 

 centre of the tail. The elongation of the nucleus and the tailpiece con- 

 tinues, and is accompanied by a reduction of the " centrosome,'' which 

 finally becomes extremely small. 



17. The head of the spermatozoon is composed of the nucleus ; the 

 " centrosome " forms the middle piece, and the axial filament and its sur- 

 rounding cytoplasm form the tail. 



18. The spermatids travel later towards the posterior end of the follicle 

 with their heads turned towards the anterior end ; and this phenomenon is 

 observable in the spermatozoa. The spermatids are found scattered in the 

 follicle, the unripe spermatozoa in more closely associated clusters, and the 

 ripe spermatozoa in solid bunches. 



19. At no stage have I observed a discharge of chromatin from the nucleus, 

 and I have seen nothing to suggest that the whole of the chromatin is not 

 directly concerned with the transformation from the resting reticulum to the 

 compact chromosome condition of the metaphase. 



20. The extreme posterior end of the follicle contains numerous degene- 

 rating cells, in which irregularly shaped masses of chromatin stain deeply 

 with the iron hsematoxylin. 



21. Although the individuality of the chromosomes is completely lost in 

 the resting-stages of the spermatogonia, spermatocytes, and spermatids, with 

 the one exception of the heterotropic chromosome in the primary spermato- 

 cyte growth-period, there is strong reason for supposing that the same 

 elements appear on the successive mitotic spindles throughout development. 

 It is possible that the component granules of a particular chromosome are 

 not the same in these cases, for an exchange of chromatin particles may 

 occur during the reticulum stages, and if this occurs we have at present no 

 means of discovering the extent of this exchange. It must, therefore, not be 

 assumed that corresponding chromosomes of two successive metaphases 

 contain the same individual chromomeres. 



In conclusion, I offer my thanks to Prof. Hickson and his staff for placing 

 the research laboratories of Victoria University at my disposal, and for the 

 encouragement that I have received in carrying out this research. 



Bibliography. 



Batjmgartner, W. J, 



1902. Spermatid Transformations in Gryllus assimilis. Kans. Univ. Sci. Bull. vol. i. 



1904. Some New Evidences for the Individuality of the Chromosomes. Biol. Bull, 

 vol. viii. 

 LINN. JOURN. — ZOOLOGY, VOL, XXXIL 2 



