INHERITANCE 235 



material in the egg and in the spermiae. This proportion 

 is very different in the two sexual products, as we know, 

 there being an enormous preponderance of the protoplasm 

 in the egg, of the nucleus in the spermatozoon. This seems 

 to indicate that the proportion between protoplasm and 

 nucleus is fairly indifferent for inheritance, as all the facts 

 go to show that inheritance from the father is as common 

 as inheritance from the mother. It is in the nucleus, and 

 in the nucleus alone, that any similarity of organisation 

 exists between the two sexual products, so very different 

 in all other respects : therefore the nucleus should be the 

 organ of inheritance. The phenomena of nuclear division, 

 of karyokinesis, which are quite equal in both sexual cells, 

 are certainly well fitted to support this hypothesis. 



There seems indeed to be some truth in this reasoning, 

 but nevertheless it must remain hypothetical ; and it must 

 never be forgotten that there may be very probably some 

 sort of morphogenetic importance in protoplasm also. Eauber 

 and afterwards Boveri 1 have tried to prove experimentally 

 that it is on the nuclear chromatic substance only that 

 inheritance depends, but the first of these authors failed 

 to get any results at all, and the latter obtained only am- 

 biguous ones. Godlewski, on the contrary, has fertilised 

 purely protoplasmic egg-fragments of the sea-urchin with 

 the sperm of quite another group of Echinoderms, and 

 obtained in spite of that a few stages of development of the 



' Boveri tried to fertilise enucleated fragments of the egg of Sphaerechinus 

 with the sperm of Echinus. He failed to get any results in isolated experi- 

 ments, but found a few small larvae of the pure Echinus type in large 

 cultures consisting of shaken eggs. But later experiments on hybridisation 

 in sea-urchins have shown that a full hybrid of Echinus and Sphaerechinus 

 may be purely paternal also. 



