Mat 14, 1915] 



SCIENCE 



707 



face layer of the egg, whicli may or may not 

 result in a membrane formation, starts the 

 development of the egg? The writer had 

 found that the fertilized egg can not develop 

 if deprived of oxygen, but that develop- 

 ment begins again instantly if oxygen is 

 admitted. From this and other observa- 

 tions he concluded that fertilization by 

 sperm as well as artificial membrane forma- 

 tion induced development by raising the 

 rate of the oxidations in the egg, and this 

 surmise was confirmed by actual measure- 

 ments by 0. Warburg as well as by Was- 

 teneys and the writer." It was found that 

 the entrance of a spermatozoon into the 

 egg raises the rate of oxidations from 400 

 per cent. (Arhacia) to 600 per cent. 

 {Strongylocentrotus purpuratus) and that 

 artificial membrane formation by butyric 

 acid raises the rate of oxidations to exactly 

 the same amount. 



The changes which determine this char- 

 acteristic rise in the rate of oxidations of 

 the egg are situated at the surface of the. 

 egg, in its cortical layer. The process 

 underlying membrane formation can be 

 called forth by any substance which causes 

 cytolysis — that form of destruction of the 

 cell which results in the transformation of 

 a cell into a mere shadowy skeleton. Any 

 cytolytic agent will induce membrane 

 formation and also development in the un- 

 fertilized egg, if it is allowed to act on the 

 superficial layer of the egg only, i. e., if the 

 egg is removed from its influence after the 

 membrane formation. If it is not removed 

 the whole egg will undergo cytolysis and 

 can no longer develop. But such eggs will 

 still show the rise in the rate of oxidations 

 which follows artificial membrane forma- 

 tion, thus indicating that the sudden rise in 

 the rate of oxidations which we notice after 



6 There are indications that other processes are 

 also initiated or accelerated by fertilization, but 

 this may be omitted from consideration in this 

 connection. 



artificial membrane formation depends only 

 upon the alteration of the surface of the 

 egg, regardless of the condition of the rest 

 of the egg. 



The forces which induce the egg cell to 

 develop are, therefore, localized at the sur- 

 face of the cell and consist in a change 

 (possibly a cytolysis) of the cortical layer 

 of the egg. We do not know how this 

 change induces the rise in the rate of oxida- 

 tions upon which development depends, but 

 from Warburg's work it appears probable 

 that the oxidations in the sea urchin egg 

 are due to a catalysis by iron. This would 

 indicate the possibility that in the cytol- 

 ysis of the cortical layer of the egg the iron 

 would be transformed from a condition 

 where it is unable to act as a catalyzer into 

 a condition where it can act in this capacity. 



We have mentioned the fact that all 

 cytolytic agencies call forth the membrane 

 formation in the unfertilized egg. Such 

 cytolytic substances (the lysins of the bac- 

 teriologist) are also contained in the blood 

 and cell extract of each animal; only with 

 this limitation that the cells of our own 

 body are immune against the action of our 

 own lysins, but not against the lysins in the 

 blood and cell extract of other animals. I 

 was able to show that we can call forth 

 membrane formation and development in 

 the sea urchin egg with foreign blood, e. g., 

 ox blood, or with the extracts of foreign 

 tissues, btit not with their own blood or 

 tissue extract. Wasteneys and the writer 

 could show later that this method can be 

 applied generally for artificial partheno- 

 genesis. This immunity of the egg towards 

 the lysins of its own body we may explain 

 on the assumption that the lysins contained 

 in foreign blood can enter the cell, while the 

 latter is impermeable for the lysins con- 

 tained in the blood or tissue extract of the 

 same species. If it were not for this immu- 

 nity, all the eggs would be induced to 



