148 ON THE SPERMATOGENESIS OF THE SILK-WORM. 
The investigations of vom Rath (28) on the spermatogenesis 
of Gryllotalpa and of Hcecker (12) on the egg-formation of 
Cyclops and Canthocamptus, correspond very well with Hert- 
wig’s results, and Weismann 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. Ishikawa’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. 
j Henking’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. 
