A Hit-or-Miss Universe 



323 



It has been found to be due to the 

 fact that each species possesses pro- 

 teins which differ from those of every 

 other species; but at the same time it 

 possesses also a genus-protein, which 

 is shared by other species of the same 

 genus, but differs from that of all other 

 genera. The heredity of genus and 

 species may be safely considered as 

 due to the transmission of distinctive 

 proteins; and there is some reason to 

 think that these proteins are not car- 

 ried in the chromosomes, or even in 

 the nucleus of the germ cell. They 

 may rather be located in the cytoplasm 

 of the egg-cell. In any case, the 

 specificity of life is found to be due to 

 definite chemical causes, and not to 

 anything mystical. 



3. Fertilization of the egg and the 

 commencement of its development are 

 treated at some length, but the details 

 are too technical to be srmimarized 

 readily. Dr. Loeb's general conclu- 

 sion is that there is nothing about these 

 processes which need be considered out- 

 side the sphere of scientific knowledge. 



PARTHENOGENESIS 



The experiments on artificial parthe- 

 nogenesis, which have mainly estab- 

 lished Dr. Loeb's prestige in the eyes 

 of the layman, are reviewed in this 

 connection. Fertilization of the egg 

 had been considered to consist of the 

 union of two nuclei; but when it was 

 shown that development could equally 

 well be started by chemical solutions, 

 by sticking a needle into an egg, or by 

 injecting blood into it, biologists were 

 forced to abandon the idea that the 

 union of the two nuclei was the essen- 

 tial part. It was easy to understand 

 that the primary function of the male 

 cell was to furnish a stimulus — a very 

 simple one, obviously, if the successful 

 substitutes are considered. 



Artificial parthenogenesis has been 

 successful not only with numerous in- 

 vertebrates, but with anunals as high 

 in the scale as a frog; and with at least 

 one plant. Dr. Loeb thinks there is 

 no inherent impossibility about such 

 development in the warm blooded ani- 

 mals as well. The objection that eggs 

 thus stimulated could not be made to 



develop beyond the earlier stages, has 

 now been remedied by improved tech- 

 nique; Delage brought a sea urchin to 

 maturity by artificial parthenogenesis. 



A FATHERLESS FROG 



This frog was raised by Dr. Loeb 

 from an egg-cell which had 

 been "fertilized" merely by 

 jabbing it with a fine needle. 

 It is shown actual size. Ac- 

 cording to Dr. Loeb, it was 

 no different from ordinary 

 frogs which result from the 

 union of two germ-cells. 

 The spermatozoon can be en- 

 tirely disDcnsed with in this 

 way, but the egg-cell cannot; 

 hence it appears to Dr. 

 Loeb that the egg-cell pro- 

 duces the embryo in the 

 rough, and that the sperm- 

 cell adds only more or less 

 superficial characters. (Fig. 

 19.) 



and Loeb himself has very recently 

 succeeded in bringing a fatherless frog 

 to full size. The frogs, which result 

 from the union of an egg-cell and a fine 

 needle, can in no way be distinguished 

 from frogs produced in the natural way 

 by the union of an egg-cell and a sperm- 

 cell. But while the egg-cell can thus 

 be made to develop into an adult, with- 

 out uniting with a sperm-cell, it has in 

 no case been possible to produce devel- 

 opment of a sperm-cell without union 

 with an egg-cell. 



From these facts two conclusions 

 stand out prominently: (a) that the 

 fundamental effect of the sperm-cell is 



