I48 ON THE SPERMATOGENESIS OF THE SILK-WORM. 



The investigations of vom Rath (28) on the spermatogenesis 

 of Gryllotalpa and of Hceckcr (12) on the egg-formation of 

 Cyclops and Canthocamptus, correspond very well with Hert- 

 wig's results, and Wcismann summarises the facts in the follow- 

 ing words : " In all those species which have been investigated 

 for this purpose, the germ-cells are formed by the mother- 

 cell undergoing two consecutive divisions, each of which results 

 in a halving of the number of idants, one half passing into 

 the one daughter-cell, and the other half into the other. In 

 the second division this would lead to the presence of only a 

 quarter of the original number of idants, if the number in the 

 mother-cell were not doubled by each idant becoming split into 

 two before the first division takes place. Thus there is first 

 a doubling, and then a halving, of the number of idants. I 

 consider this remarkable and apparently useless process of the 

 doubling and two subsequent halvings of the idants as a method 

 of still further increasing the number of possible combinations 

 of idants in the germ-cell of one and the same individual, and 

 have given reasons for this opinion in the above named essay." 



Prof. Ishikaica's results on the reproductive elements of 

 Diaptomus sp. also correspond with the results of the above 

 named authors except the mode of division, in which he describes 

 the transverse constriction of the chromosomes in the first divi- 

 sion of the sperm-mother-cells giving rise to dumb-bell-shaped 

 bodies. 



H Hiking's researches on the genital elements of many insects 

 (16, 15) are different from the results of all the above named 

 authors, in the time of the reduction of chromosomes. According 

 to this author the reduction of chromosomes takes place in the 

 first division of the spermatocytes or sperm-mother-cells and 

 no doubling of chromosomes takes place in the growing stage 

 of these cells, while their second division is to be looked upon 

 as the " Equationstheilung." 



In Bombyx mori, as stated above, twently-eight chromo- 

 somes are found in the primary germ-cells. In the growing 

 stage I could not detect any longitudinal splitting or the doubl- 

 ing of the number of chromosomes as vom Rath gives it in the 

 sperm-mother-cells of Gryllotalpa (28). Here I am more in- 

 clined to agree with Henking (15) who denies its occurrence. 



