I38 ON THE SPERMATOGENESIS OF THE SILK-WORM. 



change so as to form a granulated ball with a free plasm around 

 them (fig. 62 d, n). Along with these changes, the chromosomes 

 gradually separate from one another and arrange themselves at 

 the periphery of the nucleus. Figs. 63 and 64 are drawn from 

 fresh specimens treated with acetic acid methyl-green. Chromo- 

 somes collect near the nuclear wall and present a moniliform 

 appearance in a side view. The fully grown "Nebenkern" (n) 

 and mitosomes (in) are seen, one of the latter surrounded by a 

 free plasm. In fig. 64 beside the " Nebenkern " and mitosomes, 

 a row of microsomes is to be seen running through the axis of 

 the tail. A further stage with a more elongated head and a 

 pretty long tail is represented in figs. 65-83. 



In fig. 65 is given the head of a spermatozoon at a some- 

 what advanced stage. Cbromosomes are as in the first stage 

 arranged at the periphery of the nucleus, while the " Neben- 

 kern " appears more compact than before, slightly presenting 

 its granular structure. The position of mitosomes is very irregu- 

 lar, being placed either below or above the " Nebenkern " (figs. 

 65, 66 b, 68, 70, 71). 



Sometimes we see that it is situated at the extreme point of 

 the head of a spermatozoon anterior to the nucleus (fig. 67 m). 



Beside these structures there are to be seen some other 

 granulated spots, which are sometimes coagulated into a single 

 mass, sometimes scattered more irregularly (figs. 65, 68, 71, 

 72). These phenomena are very similar to those described by 

 H eiiking in Pyrrhocoris (25). Gradually these "Nebenkern" 

 elongate into the structure of the tail-part (figs. 68, 6g, 70, 71, 

 72, n). In the cross section of the tail passing through the 

 " Nebenkern" of this stage, radial processes are seen from the 

 "Nebenkern" to the wall of the tail of the spermatozoa (fig. 

 70 b, 1-2). 



The "Nebenkern" elongates more and more, becoming thin- 

 ner, and with this change, the mitosome gradually becomes fainter 

 and smaller. The radial processes of the "Nebenkern " disappear 

 (figs. 73, 77). In fig. 73 a cross section of the median part of 

 the tail with a " Nebenkern " in the centre of it, is represented. 



Hand in hand with this change, chromosomes gradually 

 accumulate at the one side of the periphery of the nucleus. This 

 accumulation presents a somewhat crescent shaped figure, but the 



