XTI.] CONJUGATION AND SEXUAL REPRODUCTION. 1 39 



•doubling of the idants (chromatosomes) and their subsequent 

 reduction to half. Furthermore, the observations of Flemming 

 on the formation of spermatozoa in the salamander prove that 

 there is an initial increase of the nuclear loops to double the 

 normal number. These facts enable us to recognize a relation- 

 ship, which Hertwig has already propounded in his account of 

 the type of ' reducing division ' met with in Ascaris. Platner 

 had previously recognized the homology between the formation 

 of spermatozoa and of ova, between the two divisions of the 

 sperm-mother-cell and the formation of the two polar bodies. 

 Inasmuch as these homologies have been proved to exist in a 

 worm, in insects, and in a vertebrate, and since also that 

 double division which leads to the extrusion of the two primary 

 polar bodies is certainly a character common to the Metazoa, 

 we may well believe that we are dealing with a process of 

 general significance, and one which is repeated during the 

 formation of the sexual cells of, at any rate, all the higher 

 Metazoa, in essentially the same way. 



Hence, after writing the remarks which appear above, I was 

 much astonished by Henking's pamphlet on the formation of 

 ova and spermatozoa in an insect, Pyrrhocoris apterus, in which 

 the process is described as following an entirely different plan. 

 The observations are clearly exact and trustworthy, and if the 

 author's explanation be valid, it is impossible to attach to the 

 processes of maturation in this insect a meaning similar to that 

 found in the other animals which have been studied. I believe, 

 however, that Henking's interpretation is erroneous on one 

 point, and that the apparently profound differences can be 

 reconciled, in fact that they are beautifully adapted to make 

 clear the essential parts of the process. 



The difference between the formation of spermatozoa in 

 Pyrrhocoris and Ascaris depends upon the fact that, in the 

 former, there is no doubling of the idants before the first divi- 

 sion of the sperm-mother-cell, yet the first division takes place 

 as it does in Ascaris, so that the existing number (24) of idants 

 is halved, twelve passing to each daughter-nucleus. The latter 

 then enters upon the second division in the usual manner, each 

 of the twelve idants splitting longitudinally, and their halves 

 passing into the grand-daughter-nuclei. These last grand- 

 daughter-cells constitute the sperm-cells, and the final result of 



