2OO C. M. CHILD. 



doubted from my own observations as well as those of others 

 that the development of the spermatozoon in these forms differs 

 in certain respects from the typical method. Although the 

 greatest caution has been observed throughout, the observations 

 are given with a certain reserve, because it was impossible to 

 attain complete certainty on many points and because they are 

 not in accord with commonly accepted opinions regarding the 

 development of the spermatozoon. I believe, however, that a 

 careful investigation of spermatogenesis in the cestodes will prove 

 of interest. 



Except in the early stages when the spermatid nuclei produced 

 mitotically appear in pairs about the cytophore (Fig. 42, PI. XIV.) 

 and those arising by fragmentation of the spermatocytes are 

 massed in the interior of the cytophore (Figs. 34-36, PI. XIII.) 

 there is no certain criterion for distinguishing the two kinds. The 

 presence of old nucleoli in a cytophore render it probable that 

 all or a part of the spermatid nuclei of that cytophore have 

 arisen by fragmentation, but beyond this no means of identifying 

 the nuclei of different origin has been discovered. 



The following account concerns the spermatids without respect 

 to origin. If my conclusions are correct, however, many of 

 these may be the results of fragmentation. As was noted above, 

 developing spermatozoa not different in appearance from others 

 have often been found on cytophores containing the old nucleoli. 



Figs. 42 and 43 (PI. XIV.) show the newly formed spermatid 

 nuclei after mitosis. In Fig. 43, from M. pianissimo,, five chro- 

 matin granules are distinctly visible in each of the nuclei. 

 These may represent five chromosomes : it is possible that the 

 spermatocytes of this species contained only five dyads (Fig. 

 16, A, PI. XI.) and that the cases where a larger number seemed 

 to be present (Figs. 16, B, 16, C, PI. XI.) were only earlier 

 stages before the chromatin had become massed in the dyads. 



After the formation of the spermatid nuclei their peripheral 

 position on the cytophore becomes more and more marked until 

 finally each is borne on a short peduncle or stalk of cytoplasm 

 (Fig. 44, PI. XIV.). The cytophores differ greatly in size 

 according as they were formed from a single spermatocyte or a 

 larger number : in fact in older testes single isolated spermatids 



