Manchester Memoirs, Vol. Ixii. (191 7), No. 2 31 



Theory of Delarge. 



Delarge was one of the first to undertake work on artificial 

 parthenogenesis. In 1901 he tried the effect of various chloride 

 salts on the eggs of starfish and ;sea urchins, and obtained de- 

 velopment up to the blastula stage. The theory with which he is 

 associated, however, was developed as a continuation of his 

 views in regard to the mechanism ,of cell division. In 1898 

 Montgomery showed tha ( t it was not necessary for the male and 

 female pronucleus to< fuse in order for development to take 

 place. Delarge extended this observation by a series of others 

 in which he wais able to get fertilisation of enucleated pieces 

 of egg. 



Cell division is, according to this observer, a series of coagu- 

 lations ahd liquefactions of the colloidal protoplasm. This con- 

 ception was then extended toi account for artificial partheno- 

 genesis. As acids are usually coagulators and alkalies liquefiers 

 of protoplasm, Delarge treated unfertilised eggs first with HJC1 

 and then with ammonia ; by this means development was induced. 

 In later experiments tannin was employed as the coagulating 

 substance, with much better results, for by this method develop- 

 ment proceeded to' its final stage and young sea urchins were 

 obtained. 



Later in the investigations tannate of ammonia was used with 

 good results. This was explained by saying that the tannin was 

 a feeble acid and the ammonia a base; when in solution separa- 

 tion occurred between the two' substances and each worked 

 separately. 



In comparison with the work of Loeb', it is of interest that 

 Delarge demonstrated that the presence of free oxygen was 

 unnecessary for inducing parthenogenesis, and also that a hyper- 

 tonic solution was not of vital importance. 



The theory is different from Loeb's in that there is not called 

 into play any special chemical substances. The substances neces- 

 sary for development are already resident in the egg and only 

 require to be set into motion. According to Loeb, the necessary 

 stimulus for this is the chemical substances brought in by the 

 sperm, according to Delarge the substances will arrange them- 

 selves in the requisite manner under the influence of molecular 

 forces. The nuclear membrane, centrosomes, achromatic spindle 

 and the chromosomes are transient features of the cell, appear- 

 ing and disappearing in the protoplasm as though they were in 

 a state of a sol or a gel. Thiej agents employed for artificial 

 parthenogenesis then act as coagulators and liquefiers, thus pro- 

 ducing a series of coagulations and liquefactions which culminate 

 in development. The feeble point in the theory is that these 



