The Mechanistic Conception of Life 



11 



egg, as A. P. Mathews found in the case of star-fish eggs and I 

 in the case of the eggs of certain worms. In the case of the 

 eggs of the frog it suffices to pierce the cortical layer with a 

 needle, as Bataillon found in his beautiful experiments a 

 year ago.^ The mechanism by 

 which development is caused 

 is apparently the same in all 

 these cases, namely, the de- 

 struction of the cortical layer 

 of the eggs. This can be 

 caused generally by certain 

 chemical means which play a 

 role also in bacteriology; but 

 it can also be caused in special 

 cases by mechanical means, 

 such as agitation or piercing of 

 the cortical layer. It may be 

 mentioned parenthetically that 

 foreign blood sera have also a 

 cytolytic effect, and I succeeded 

 in causing membrane formation and in consequence the devel- 

 opment of the sea-urchin egg by treating it with the blood of 

 various animals, e.g., of cattle, or the rabbit. 



Recently Shearer has succeeded in Plymouth in causing a 

 number of parthenogenetic plutei produced by my method to 

 develop beyond the stage of metamorphosis, and Delage has 

 reported that he raised two larvae of the sea-urchin produced 

 by artificial parthenogenesis to the stage of sexual maturity. 

 We may, therefore, state that the complete imitation of the 

 developmental effect of the spermatozoon by certain physico- 

 chemical agencies has been accomplished. 



I succeeded in showing that the spermatozoon causes the 

 development of the sea-urchin egg in a way similar to that 



1 This method does not work with the eggs of fish and is apparently as limited 

 in its applicability as the causation of development by mechanical agitation. 



Fig. 10. — Pluteus stage of Strongy- 

 locentrotus purpuratus. S skeleton; 

 D intestine. 



