ON THE SPERMATOGENESIS OF THE SILK-WORM. I37 



mass collecting in the centre of a nucleus, but no resting stage 

 is formed. The fate of the centrosomes is not known. The 

 collected chromosomes gradually separate from one another and 

 form a loose mass of chromatin granules. 



A full grown spindle with a " Kernplatte " is again formed. 

 Owing to the reduced size of the cell-body after the first division 

 (compare figs. 51 and 52 with figs. 54 and 55 all of which are 

 magnified to the same diameter), the spindle together with that 

 of the individual chromosome is very small in this spindle, so 

 that we can easily distinguish it from the spindle of the first 

 division. A side view of a cell in this second division is shown 

 in fig. 54. In this division, the chromosomes are arranged in a 

 single row, and no constriction is to be seen in any of them. In 

 the polar view of the " Kernplatte," twenty-eight chromosomes 

 can be counted (fig. 55). These separate into two groups and 

 form the chromosomes of sperm-daughter-cells, each of which 

 therefore contains fourteen chromosomes. Fig. 56 represents the 

 diaster of this stage. The exact number of the chromosomes 

 can not be made out in the side view, but in the polar view we can 

 clearly count fourteen (fig. 58). Sometimes, a darker structure, 

 somewhat resembling the " Verbindungsbriicken," is to be seen 

 under the polar spindle (fig. 57, lower figure), but I am not able 

 to tell what this really represents. 



A single or a double row of cell-plates appear at the equator 

 of the " Verbindungsfaden " (Figs. 58, 59,60) and the cell be- 

 comes constricted. The central and the polar spindles can now 

 be clearly distinguished from one another (Fig 59). The former 

 appears as a compact mass presenting a median darkly stainable 

 part, while the polar spindle forms a somewhat semicircular 

 ring having a centrosome in its centre. 



The daughter-cells, after these changes, completely separate 

 from each other. These we call sperm-daughter-cells which 

 correspond with the " Spermatides " of la ValetteSt. George. 



IV. The Stage of Metamorphosis. In this stage, the sperm- 

 daughter-cells gradually change themselves into spermatozoa. In 

 figs. 61 and 62 we have five sperm-daughter-cells. The "Verbin- 

 dungsfaden " gradually contracts, accumulating in its end some 

 microsomes (fig. 62 a, b). These " Verbindungsfaden " become 

 gradually coarser, as is represented by fig. 62 c, m, and finally 



