64 THE PHYSICAL BASIS OF INHERITANCE 



which we have elsewhere expressed, that life is a function of inter- 

 relations, we confess to hesitation in accepting without saving clauses 

 any attempt to call this or that part of the germinal matter the 

 exclusive vehicle of the hereditary qualities. 



2. The sperm-nucleus brings with it into the ovum a little cyto- 

 plasm, and it is also accompanied by the minute central corpuscle 

 or centrosome, which seems to play an important part in regulating 

 the mechanism of cleavage. It may be that the minimal quantity 

 of cytoplasm is also important, though we cannot trace its behaviour 

 as we do that of the centrosome. Strasburger says that if it were 

 important there would be more of it, but in these matters size and 

 mass seem of small moment ; the little cytoplasm there is may act 

 like the little leaven which leavens the whole lump. It seems in 

 this connection very desirable that the experiments which have 

 been begun (Fieri and Winkler) of extracting a ferment (" ovulase ") 

 from seminal matter and using it as a fertilising agent, should be 

 confirmed or confuted. 



3. In Loeb's experiments unfertilised sea-urchin's eggs developed 

 into complete and normal larvae ; the sperm-nucleus was dispensed 

 with. In Delage's experiments non-nucleated fragments of the 

 ova of sea-urchin, worm, and mollusc were fertilised and developed 

 into normal larvae ; the ovum-nucleus was dispensed with. But 

 it must be noted carefully that in both cases there was a nucleus 

 present. 



4. Hickson (1907) has argued forcibly in support of the view that 

 " for the present at any rate we can only say that the germ-cells 

 as a whole, and not any special part, are responsible for the trans- 

 mission of heritable characters from generation to generation." He 

 suggests speculatively that the more plastic characters may be 

 transmitted mainly by the cytoplasm and the rigid characters by 

 the nucleus. In his criticism he refers to cases where chromosomes 

 are quite indistinct in the gametes, to the importance of cytoplasm- 

 fusion in the conjugation of some Protozoa, to the experiments of 

 Herbst and Fischel on hybridisation in Echinoderms, which indicate 

 the importance of the cytoplasm of the ovum in transmitting 

 characters, and to other sets of facts which indicate the danger of 

 exaggerating the importance of the chromosomes. The observations 

 of Godlewski are also strongly suggestive of the importance of the 

 cytoplasm, as well as the nucleus, in inheritance. 



5. Bateson (1907) has pointed out that if the chromosomes were 



