THE GERM-PLASM THEORY \ {) \ 



cell in which they become active, causing it to ™ry in such a „. 

 that the formation of the relevant pari results. While I cone 

 development as a continuous process, I supplement this with the i 

 that from within, namely, from the nuclear substance, new, din 

 'determining' influences are continually being exerted on thi 

 veloping cells. 



I can hardly think of a better proof of the necessity of tin- 

 assumption than that furnished by Delage, one of the mi ate 



biologists of France, who, in his comprehensive book on Hi 

 striven to replace the theory of determinants by something simpler. 

 Delage rejects all 'primary constituents' (Anlagen) in th< 

 ' particules representatives,' as much too complicated an assumption, 

 and thinks it possible to work with the conception of a germ-pla 

 which is about as simple as the cell-substance of a Rhizopod, thai 

 to say, a protoplasm of definite chemico-physical constitution and 

 composition. Leaving out of account the consideration thai the 

 protoplasm of an amoeba is scarcely of such extreme simplicity, but 

 is certainly made up of numerous differentiated and definitely 

 arranged biophors, how could such an extremely simple (' eminemment 

 simple') constitution of the ovum as is here assumed give rise to such 

 a complicated organism, the individual parts of which are capabl 

 independent and transmissible variation? According to Delage it 

 does so because the ovum, though not containing -all tin- fad 

 requisite for its ultimate resultant,' does contain ' un certain nombre 

 des facteurs ne'eessaires a la determination de chaque partie el d<- 

 chaque caractere de l'organisme futur'! Determinants after all, it 

 may be said, but that is far from the truth ! It is not primary con- 

 stituents that the germ contains, according to Dclagr. it i- clii-inica] 

 substances, for instance muscle substances, probably 'les substani 

 caracteristiques des principales categories de cellules, e'est-a-dire, 

 celles qui, dans ces cellules, sont la condition principale de leur fonc- 

 tionnement.' All these must be contained in the ovum. How tl 

 are to reach their proper place in the organism. 1p>\\ the 'charac- 

 teristic chemical substance ' of a mole is to land just behind the right 

 or left ear of the fully formed man, is not stated. But apart from 

 this, there is a much deeper error in this assumption of Bpecitic 

 chemical substances in the ovum as an explanation of the phenomei 

 of local hereditary variation, and I have already touched upon 

 chemical substances are not vital units, which Peed and reprodu 

 which assimilate and which bear a charm against the assimilating 

 power of the surrounding protoplasm. They would necessarily 

 modified and displaced in the course of ontogeny, and would therefore 



