86 ~ S. GOTO. 



the development of spermatozoa from the mother-cells ; and a glance 

 at them will convince one that spermatogenesis mxist be effected in 

 this group in a manner quite different from what we are wont to see 

 in others. I have endeavoured to trace the various stages of sper- 

 matogenesis, and although I have not come out perfectly clear in every 

 point of detail, still I believe I can communicate the result as being in 

 the main correct. I have represented the various stages in fig. 3, PI. 

 VI, as found in Microcotyle caudata. The various zones that have 

 been described by recent writers in the genital glands can not be 

 distinguished in tlie testes of the ectoparasitic Trematodes ; on the 

 contrary, the sperm mother-cells as w^ell as the spermatozoa in various 

 stages of development are, as already stated, mingled pell-mell. The 

 youngest stage is probably that of the small nuclei already referred to 

 as forming a group, each having a finely granular cytoplasm of its own 

 (PI. VI, fig.. 3, a) and containing a small number (4 or 5) of 

 chromatin granules. These nuclei grow larger and larger, and the 

 chromatin granules increase in number and also more or less in size ; 

 the cytoplasm, however, seems to remain almost constant, and in the 

 stages represented in b and c it forms an inconspicuous thin layer 

 around each nucleus. The individual nuclei become more and more 

 detached from one another ; but I have sometimes observed them in 

 these stages wtill kept together by a common mass of protoplasm (cJ). 

 The nuclei still grow and grow, and the chromatin granules increase 

 considerably in number (e) ; and although I have not been able to 

 observe the intermediate stage, these granules must come either to 

 form a reticulum and then a single thread, or passing over the i-e- 

 ticulum stage form directly the single thread. The stage which I take 

 to be the next is represented in/. Here the chromatin forms a single 

 thread coiled so as to form numerous loops, and, so far as I have 

 observed, having no end ; the nuclear membrane has also disappeared 



