FERTILIZATION 169 



water. Their further development into gastruls and plutei occurred 

 with the same velocity as that of the control eggs, which had been fer- 

 tilized by sperm; and the larvae showed an equal degree of vitality. 

 It is an easy matter to produce and collect an unlimited number of plutei 

 from the eggs treated with this method. 



When the eggs are taken out too early from the acidulated sea water, 

 they form no membrane, and the same is true when they remain too 

 long in the acidulated sea water. If eggs that have been treated with a 

 fatty acid without forming a membrane are submitted to the hypertonic 

 sea water for from: twenty-five to fifty minutes, they will not develop into 

 larvae, and not even segment. It is therefore obvious that the membrane 

 formation and not the treatment with acid is responsible for these effects. 

 This is corroborated by some further observations. 



O. and R. Hertwig discovered that if sea water is saturated with 

 chloroform — only traces of which are soluble in water — the unfertil- 

 ized eggs of the sea urchin form a membrane when put into this chloro- 

 form sea water.* Herbst found that benzol, toluol and creosote act 

 similarly.f It seemed to me that possibly hydrocarbons in general 

 might act in this way, and as a test I used amylene. It indeed called 

 forth the membrane formation. This method of calling forth a mem- 

 brane formation by hydrocarbons has a serious drawback, inasmuch as 

 the eggs show a tendency to undergo cytolysis, and are killed. By the 

 speedy transportation of the eggs into normal sea water some may be 

 saved. 



It seemed of interest to ascertain whether it made any difference for 

 the parthenogenetic development which substance was used for the pro- 

 duction of the membrane. When the eggs were taken immediately after 

 the formation of the membrane from the sea water containing benzol, 

 not all the eggs that had formed a membrane underwent cytolysis. 

 When these eggs were subsequently treated in the way described above 

 with hypertonic sea water, they segmented, and some of them developed 

 into plutei. As long as the formation of a membrane is induced by a 

 substance which does not injure the egg too much, the subsequent short 

 exposure to hypertonic sea water may lead to the formation of an em- 

 bryo. In regard to their vitahty, and possibly their structure, the em- 

 bryos may possibly differ according to the substance which is used for 

 the production of the membrane. This, however, must be determined 

 by further experiments. 



It agrees further with the idea that the membrane formation and not 



* O. and R. Hertwig, Untersuchungen zur Morphologic und Physiologic der Zelle, Heft 

 S, Jena, 1887. 



t Herbst, Biologisches Centralblatt, Vol. 13, p. 14. 1893; and Mittheilungen aus d. 

 Zool. Station Neapel, Vol. 16, p. 445, 1904. 



