Action of blood on eggs 253 



lipoids, in the cell. If this view is correct, it would be necessary to 

 ascribe the fertilisation of the egg to the same process. 



The analogy between haemolysis and fertilisation throws, 

 possibly, some light on a curious observation. It is well known 

 that the blood corpuscles, as a rule, undergo cytolysis if injected 

 into the blood of an animal which belongs to a different family. 

 The writer found last year that the blood of mammals, e.g. the 

 rabbit, pig, and cattle, causes the egg of Strongylocentrotus to 

 form a typical fertilisation-membrane. If such eggs are afterwards 

 treated for a short period with hypertonic sea-water they develop 

 into normal larvae (plutei). Some substance contained in the 

 blood causes, presumably, a superficial cytolysis of the egg and 

 thus starts its development. 



We can also cause the development of the sea-urchin egg without 

 membrane-formation. The early experiments of the writer were 

 done in this way and many experimenters still use such methods. It 

 is probable that in this case the mechanism of fertilisation is essen- 

 tially the same as in the case where the membrane-formation is 

 brought about, with this difference only, that the cytolytic effect is 

 less when no fertilisation-membrane is formed. This inference is 

 corroborated by observations on the fertilisation of the sea-urchin 

 egg with ox blood. It very frequently happens that not all of the 

 eggs form membranes in this process. Those eggs which form 

 membranes begin to develop, but perish if they are not treated with 

 hypertonic sea-water. Some of the other eggs, however, which do 

 not form membranes, develop directly into normal larvae without any 

 treatment with hypertonic sea-water, provided they are exposed to 

 the blood for only a few minutes. Presumably some blood enters the 

 eggs and causes the cytolytic effects in a less degree than is necessary 

 for membrane-formation, but in a sufficient degree to cause their 

 development. The slightness of the cytolytic effect allows the egg to 

 develop without treatment with hypertonic sea- water. 



Since the entrance of the spermatozoon causes that degree of 

 cytolysis which leads to membrane-formation, it is probable that, 

 in addition to the cytolytic or membrane-forming substance (pre- 

 sumably a higher fatty acid), it carries another substance into the 

 egg which counteracts the deleterious cytolytic effects underlying 

 membrane-formation. 



The question may be raised whether the larvae produced by 

 artificial parthenogenesis can reach the mature stage. This question 

 may be answered in the affirmative, since Delage has succeeded in 

 raising several parthenogenetic sea-urchin larvae beyond the meta- 

 morphosis into the adult stage and since in all the experiments made 

 by the writer the parthenogenetic plutei lived as long as the plutei 

 produced from fertilised eggs. 



