STUDIES ON THE EOTOPARASITIC TREMATODES OF JAPAN. ,S7 



and tlie tlirend lies in a very finely oTannlar, weakly staining' substance. 

 Then this tlircad splits int(j nunievoiis shorter ]>ieees (r/), which 

 o-radnally separate more and more from e:ich other, and hnallv 

 occupy rlie perijtliery of tlic rommi^n mass in which tliey lie imlx'd(](Ml 

 (//. /). At this stag'e each piece of chromatin lias assumed a lozeno^e 

 shape, and become intersected by small clear spaces, effectinir a 

 partial division of it into several ])arts. Tt contracts more and 

 more and finally l)ecomes a verital)le nucleus (/,) havino- a contain- 

 ing mend)rane with a few granules of chromatin (chromosomes) 

 inside. The newly fonned nuclei then repeat the very same 

 changes above described, but how manv times it is impossible to tell. 

 The small lozenge-shaped chromatin ])ieces fln;dly formed then liegin 

 to lengthen from one end (;;/). this time apparently without becoming 

 a veritable nucleus such a.s is represented in /,■. The tail continues to 

 lengthen more and more until oidy a small portion of the chromatin 

 remains as the liead, so that the ripe spermatozoon has tlie form of a 

 long pin, formed head and tail thronghout of chromatin (//) ; and all 

 the spermatozoa derived from a single mother-cell of the last gene- 

 ration f)rm a bundle, with the head imbedded in a common m;iss 

 of ftnely grannlar protoplasm. Tt may l)e, however, that the ])roto- 

 plasm f jrms an exceedingly tln'n layer around the head ;is well ;vs 

 the tail. The spermatozoa seem finally to free themselves from the 

 mass of ])rotoplasîn ; ïov I have sometimes observed similar masses 

 floating in the cavity of the testes (o). In / I have figured a stage 

 which does not seem to come in well in the above series, and which 

 I have observed only rarely. It may perhaps re]:)resent a stage im- 

 mediately prior to the one rejiresented in /.: and of exceedingly 

 short duration. In it the small nuclei hsive each n cytoplasm of its 

 own (^f |)rismatic shape. -ukI are arranged on the surf ice of a central, 

 spherical mass of prot(-)plasm, whicli is whollv destitute of ;i nucleus. 



