288 THE CELL 



which was produced by budding, receive from the two bundles of 

 four segments two daughter-bundles each containing two seg- 

 ments. 



Here also the second division follows the first so closely, that 

 the resting stage is omitted. Out of the material of that half of 

 the spindle which remained behind in the egg-daughter-cell, a 

 second complete spindle develops directly, containing only four 

 segments, arranged in pairs. A second budding produces both 

 the second polar-cell (Fig. 127 IF.), and the grand-daughter egg- 

 cell, or the mature egg, each division product containing only two 

 nuclear segments. 



If we disregard the fact that the division products, when the 

 egg is ripe, are very unequal in size (budding), the processes which 

 take place resemble so exactly those already described as occurring 

 during sperm formation, that through them some light is thrown 

 upon the raison d'etre of the polar-cells. Whilst on the one 

 hand four spermatozoa (Fig. 126 III., A, B, G) develop out of a 

 sperm-mother-cell (Fig. 126 /.), on the other only one egg capable 

 of being fertilised (Fig. 127 V.) and three abortive eggs arise out of 

 an egg-mother-cell. These latter still remain in a rudimentary 

 form, although they play a part in the physiologically important 

 division with reduction. 



It has been noticed in many other objects besides Nematodes, 

 that the mature sexual products only possess half as many nuclear 

 segments as the tissue cells of the organism in question; this was 

 observed by Boveri (VI. 6) in the mature egg-cells of the most 

 various classes of the animal kingdom, by Flemming (VI. 13 II), 

 Platner (VI. 52), Henking (VI. 27), Ishikawa (VI. 40), Hacker 

 (VI. 24), vom Rath (VI. 55), in mature spermatozoa of Salamandra, 

 Gryllotalpa, Pyrrhocoris, Cyclops, etc., and by Guignard (VI. 23 6), 

 in the nuclei of the polar-cells, which are formed during fertilisa- 

 tion, and in the nucleus of the mature egg-cell of Phanerogamia. 



Maupas (VII. 30) and Richard Hertwig (VII. 21) observed 

 that a reduction of nuclear substance occurs also in Infusoria 

 before fertilisation ; however, further details on this subject are 

 given later, on p. 269 (Chapter VII.). 



In all the above-mentioned cases, the reduction of nuclear sub- 

 stance occurs before the egg-cell is fertilised by the spermatozoon. 

 It appears, however, that the reduction of nuclear substance may 

 occur after fertilisation has taken place, as a priori appears quite 

 possible, as a result of the first division. At any rate that is the 



