LIFE AND EXPERIMENT 



stance liberated hy the eggs, but to increased salinity of 

 the sea-water.^ 



Few authors who quote Wilson's famous experiments on 

 the eggs of the marine mollusc, Patella, I think, realize that 

 Wilson never succeeded in obtaining normal fertilization. - 

 It is not improbable that the results he obtained, upon 

 which he based far-reaching conclusions which have been 

 generally accepted, were in part due to the abnormality 

 invoked by the artificial aid with which he induced fertiliza- 

 tion. To induce cross-fertilization (fertilization of eggs 

 with non-specific spermatozoa) often one has recourse to 

 artificial aid, as changes in alkalinity or temperature of the 

 sea-water. Such changes however bring about variations 

 in the development of the egg (for instance of the sea- 

 urchin) also if these develop from straight fertilization 

 (fertilization of eggs with specific spermatozoa). This 

 fact makes it clear that results obtained after cross-fertiliza- 

 tion can not be ascribed to the influence of the non-specific 

 spermatozoon or its chromosomes unless it is shown that 

 the efTect differs from that obtained in straight fertilized 

 eggs that were subjected to the same changes in the medium 

 by which the cross-fertilization was induced. Since the 

 experiments on cross-fertilization that have been made were 

 not controlled in this way, they allow no conclusion as 

 to the action of the foreign sperm-nucleus.^ 



Even under constant external conditions the sea-urchin's 

 larval skeleton will vary, as most exact stud}' of normal 

 straight fertilized eggs has shown."* Thus the extent to 



1 Just, ig2gd. 



~ Wilson, igo4. 



^ It must therefore astonish us that Morgan (/gjj) not only 

 accepts these experi?nents.on cross-fertilization but also in a zvide- 

 sweeping statement categorically declares them to be proof for action 

 of the genes on the cytoplasm. 



■^ Tennent, igio. 



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