142 ON THE SPERMATOGENESIS OF THE SILK-WORM. 



selben sich ansammeln, wahrend der iibrige Inhalt durch 

 langlich ausgezogene Tropfen gegeben ist, die sich zu varicosen 

 Faden anreichen." 



Let us now compare Verson's results with mine above de- 

 scribed. The description in his first paragraph is certainly that 

 of my primary germ-cells. The second is also primary germ- 

 cells in their later stages. The third and fourth are the cells of 

 the growing stage and similar to my sperm-mother-cells. The 

 " komma- oder hufeisenformig gestaltete Korperchen " in the 

 nucleus are undoubtedly derived from a bad preservation of the 

 materials, and seem to be caused by coagulation of the chro- 

 matin granules in the granular stage of the nucleus in young 

 sperm-mother-cells. The fifth and sixth are the cells of the 

 ripening stage. Just, as Verson stated, the sperm-mother-cells 

 are generally arranged peripherally round the inner side of a 

 cyste in a row, while after the first division such an arrange- 

 ment is completely destroyed. Between the two successive 

 divisions of the sperm-mother-cells no nucleolus appears in a 

 nucleus. Consequently his description " ihre Kerne schliessen 

 haufig scharf markirte Kernkorperchen ein " seems to be due 

 to his mistaking the coagulated mass of chromosomes for the 

 nucleolus. The seventh and eighth are the stage of metamor- 

 phosis. In this stage, he also mistakes the coagulation of the 

 chromosomes for a nucleolus. 



In general, his result agrees with that of my own investiga- 

 tion, though in the details it differs very much, probably in con- 

 sequence of his defective methods of investigation. 



Spindle Figures, "Nebenkern," Centrosomes 

 and Nucleolus. 



As to the origin of the achromatic spindle, many facts have 

 been observed by eminent naturalists such as van Benedcn, (1) 

 Flemming (7), 0. Hertwig (19), Plainer (25), Strasburger (33, 34), 

 Hermann (17), Boveri (2), Brauer (4), Waldyer (40), Rabl, (29) 

 Waiase (41) Schewiakoff (3), Ishikawa (21, 22) and many others, 

 in different animals and plants. In general, there are, as far as 

 my knowledge goes, three views as to its origin : (1) the achro- 

 matic threads arise chiefly from the cell protoplasm ; (2) they 



