2 $6 SOME ASPECTS OF CELL-CHEMISTRY AND CELL-PHYSIOLOGY 



here lie in a single series alternating with chambers of nutritive cells. 

 The latter contain granules which are believed by Korschelt to pass 

 into the egg, perhaps bodily, perhaps by dissolving and entering in a 

 liquid form. At all events, the egg contains accumulations of similar 

 granules, which extend inwards in dense masses from the nutritive 

 cells to the germinal vesicle, which they may more or less completely 

 surround. The latter meanwhile becomes amoeboid, sending out long 

 pseudopodia, which are always directed towards the principal mass of 

 granules (Fig. 58). The granules could not be traced into the nucleus, 

 but the latter grows rapidly during these changes, proving that mat- 

 ter must be absorbed by it, probably in a liquid form. 1 



All of these and a large number of other observations in the same 

 direction lead to the conclusion that the cell-nucleus plays an active 

 part in nutrition, and that it is especially active during its constructive 

 phase. On the whole, therefore, the behaviour of the nucleus in this 

 regard is in harmony with the result reached by experiment on the 

 one-celled forms, though it gives in itself a far less certain and con- 

 vincing result. 



We now turn to evidence which, though less direct than the experi- 

 mental proof, is scarcely less convincing. This evidence, which has 

 been exhaustively discussed by Hertwig, Weismann, and Strasburger, 

 is drawn from the history of the nucleus in mitosis, fertilization, and 

 maturation. It calls for only a brief review here, since the facts have 

 been fully described in earlier chapters. 



3. The Nucleus in Mitosis 



To Wilhelm Roux ('83) we owe the first clear recognition of 

 the fact that the transformation of the chromatic substance dur- 

 ing mitotic division is manifestly designed to effect a precise di- 

 vision of all its parts, i.e. a panmeristic division as opposed to a 

 mere mass-division, and their definite distribution to the daughter- 

 cells. "The essential operation of nuclear division is the divi- 

 sion of the mother-granules" (i.e. the individual chromatin-grains) ; 

 "all the other phenomena are for the purpose of transporting the 

 daughter-granules derived from the division of a mother-granule, one 

 to the centre of one of the daughter-cells, the other to the centre of 

 the other." In this respect the nucleus stands in marked contrast to 

 the cytoplasm, which undergoes on the whole a mass-division, although 

 certain of its elements, such as the plastids and the centrosome, may 

 separately divide, like the elements of the nucleus. From this fact 

 Roux argued, first, that different regions of the nuclear substance 



1 Some observers have maintained that the nucleus may take in as well as give off solid 

 matters. This statement rests, however, on a very insecure foundation. 



