THE PROBLEM OF ACTIVATION 255 



tozoon introduces a coagulating agent; the coagulation 

 is not the cause but a result of activation. 



It must already be obvious that it is difficult to 

 settle the question of priority of incidence of the physi- 

 cal and chemical changes involved in the activation of 

 the egg. A second difficulty equally great is to show 

 how these changes intervene in the physiological events 

 of activation, and a third is to show how the morpho- 

 logical sequence results as a consequence of physico- 

 chemical and physiological events. But these are 

 absolutely general biological problems, and the subject 

 of activation of the egg is probably as far advanced 

 with respect to them as any other biological problem, 

 in some respects more so. Investigation will naturally 

 follow these three directions more or less separately 

 and simultaneously. But a view that does not respect 

 all three fields will necessarily be partial and inco'mplete. 



The discussion of parthenogenetic activation would 

 be too incomplete if it did not include an account of 

 Bataillon's brilliant success (1910) in producing parthe- 

 nogenesis in the frog, and of the analysis of the results 

 by Bataillon and other investigators. As is well known, 

 this worker after years of vain attempts to induce the 

 development of frogs' eggs by parthenogenesis finally 

 succeeded by the exceedingly simple method of pricking 

 them with a fine needle. This result has been confirmed 

 by Dehorne (1911), Henneguy (1911), Brachet (1911), 

 Loeb and Bancroft (1913), McClendon (1912), and 

 Herlant (1913, 1917). As a matter of historical justice 

 it should be mentioned that this result was foreshadowed 

 by Guyer (1907) in his remarkable experiments of inject- 

 ing blood into frogs' eggs, by which some development 



