64 THE PHYSICAL BASIS OF INHERITANCE 



of a firm's success may depend upon a particularly fortunate 

 association of partners, so it may be with vitality." * " We 

 are compelled by the most stringent evidence to admit that 

 the ultimate basis of living matter is not a single chemical 

 substance, but a mixture of many substances that are self- 

 propagating without loss of their specific character." f Holding 

 firmly to this view, 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 

 cytoplasm, 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 (Pieri 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. 



* J. Arthur Thomson, Science of Life, p. 115 (London, 1899). 



t E. B. Wilson, The Cell in Development and Inheritance (1st ed., 1896). 



