Nos. IAND2.] COTYLASPIS INSIGNIS. 29 



In some, c. g.. Fig. 46. I find deeply stained spots in the cytoplasm, 

 which by more extended studies I may be able to prove to be cen- 

 trosomes ; they have the appearance and position necessary to that 

 identification, I have not succeeded in recognizing- intermediate 

 stages between 42 and 43. There are syncytia composed of 

 double the number of nuclei as 43 ; one of these is shown 

 in 44, and in these there is a more distinct indication of 

 the formation of walls between the nuclei and the cutting 

 off of the base of the cell from a central residue of the 

 original mass of cytoplasm. Fig. 47 is a stage of this in which 

 four of the cells are indicated as being in the same condition of 

 karyokinesis at the same time, viz., the metaphase. Isolated cells 

 from similar situations are shown in Figs. 48 and 49. It has not 

 been possible to study the chromosomes in detail ; there seem to be 

 a small number. I incline to identify the cells of this stage as the 

 spermatogones. They divide and double the number, as shown 

 in Fig, 44, where the cells are smaller. They show a smaller and 

 much denser nucleus, and in some cases the nuclear material is 

 drawn out into elongate shapes, as in Fig. 45, which I am inclined 

 to regard as the spermatids, early stages in the formation of the 

 spermatozoon, and thereby to identify these cells as the sper- 

 matocytes. I have only in one or two places seen indications of 

 the presence of spermatozoa, and have been inclined to suspect that 

 the season was not right for them. 



So far as I am aware the history of the spermatic cells is not 

 known for any of the Aspidobothridae and it is not recorded for 

 many of the trematodes. In so far as I am acquainted with it the 

 process in general seems much the same as here, as indicated by 

 the figures of Schwartz '86, Wright and Macallum '87, and Heckert 

 '89. In all of these parietal and central cells are found, clusters 

 of cells by division double the number from spermatogones to 

 spermatocytes and the nucleus of the latter gives rise to the sper- 

 matozoon. It is also noticeable that the precess as I have indi- 

 cated it agrees rather closely with the process as it takes place in 

 the earthworm according to Calkins '95, whose Figs. 4 and 5 bear 

 much resemblance to my Figs. 43 and 44. I find, however, that 

 the central mass, corresponding perhaps with the " blastophore " 

 of his paper, is not connected with the cells as long. In his this 



