No. 507] 



NOTES AND LITERATURE 



191 



special activities on the surrounding cytoplasm, Meves believes 

 that the differentiated parts arise by a direct metamorphosis of 

 the chondriosomes. 



Meves realizes that the nuclear substance answers fully the 

 demands of a hereditary substance, namely, that in fertilization 

 the two parts must be equivalent, that there must be a reduction, 

 and that there must be an equal division in cleavage. However, 

 he says that it has not been proved that the nuclear substance 

 and hereditary substance are identical, or that the nuclear sub- 

 stance is the only hereditary substance. He then asks the ques- 

 tion, how far do the chondriosomes satisfy conditions demanded 

 of a hereditary substance. It is evident that the quantity of 

 chondriosomes present in the egg cell is much greater than that 

 brought in by the sperm. This fact, he says, presents no great 

 difficulty, if we suppose that the specific qualities of the chon- 

 driosomes becomes expressed through the configuration of trans- 

 verse sections. According to Niigeli, an over-supply of idio- 

 plasm may be thrown out from the idioplasmic system at the time 

 of fertilization and become changed into yolk. In favor of this 

 view Van der Stricht and his students have shown that a part 

 of the mitochondria of the egg cell are changed into yolk granules. 



There is also the possibility that the male chondriosomes, after 

 entrance into the egg, multiply and divide. There is not an 

 equal division of the chondriosomes in cell division, as there is 

 of the choromatin, but they do approximate to equality of divi- 

 sion and any difference may be made good by increased growth. 



As there is a reduction of the chromatin before fertilization, 

 Meves suggests that there may be a reduction of the chondrio- 

 somes. However, he has not seen even the slightest indication 

 of a reduction, and until some evidence is forthcoming, such 

 a suggestion must remain as a mere speculation. Duesberg, 

 '07, has shown that there is a mass reduction of the chondno- 

 somes in the two spermatocyte divisions, but in the egg this is 

 not true, as the chondriosomes remain scattered throughout the 

 cell, and the resulting cells are very unequal in size. 



Meves suggests another way to prevent the increase in the 

 hereditary mass, and this is as Niigeli has shown. Niigeli supposes 

 the male and female idioplasm to unite as a mixed product. A 

 cross section through the union of the embryonic strands shows 

 that the idioplasm strands, in relation to the number of micellae 

 rows, remains unchanged. A paternal and maternal idioplasm 



