256 



SCIENCE 



[N. S. Vol. XXXVI. No. 921 



While in this way the mechanism of fertili- 

 zation was cleared up to a large extent for the 

 sea-urchin egg, very little had heen accom- 

 plished with the eggs of other invertebrates. 

 The eggs of a great many forms had been 

 caused to develop by artificial means but the 

 development was often very abnormal. 



Artificial parthenogenesis was caused in the 

 eggs of molluscs by Kostanecki as well as by 

 Loeb, but the development was abnormal in as 

 much as it resulted in the production of 

 larvae without previous segmentation. In 

 the egg of Cumingia, another mollusc, efforts 

 to produce artificial parthenogenesis had 

 failed entirely. In annelids the results were 

 not very satisfactory either. In Ghcetopterus, 

 e. g., Loeb produced parthenogenetic larvae, 

 but they developed without segmentation as 

 he first observed and as was later ascertained 

 beyond doubt by F. Lillie. 



If the lysin theory of fertilization was cor- 

 rect, it was necessary to find out whether arti- 

 ficial parthenogenesis with an approximately 

 normal type of development can be caused in 

 the eggs of all animals by foreign blood. Ex- 

 periments which we have carried on this year 

 seem to indicate that this can be done to a 

 large extent. 



m 

 We first ascertained that the eggs of Arhacia 

 behave essentially like those of Strongylocen- 

 trotus purpuraius. The eggs of Arhacia are 

 sensitized by putting them for a short time 

 into a, i M solution of strontium chloride. 

 They were then exposed for about 10 minutes 

 to ox-serum which had been rendered isotonic 

 with sea water through the addition of sodium 

 chloride. The eggs were then transferred for 

 20 minutes into hypertonic sea water. Such 

 eggs developed normally into plutei. The only 

 difference between the behavior of the eggs of 

 Arlacia and Strongylocentrotus is that the 

 eggs of Arhacia do not form a very distinct 

 membrane. It is needless to say that the 

 necessary controls were made and that we 

 made sure that the treatment of the eggs with 

 strontium choride or with strontium chloride 



and subsequently with the hypertonic solution, 

 did not lead to the formation of embryos, al- 

 though occasionally a few segmentations 

 could be brought about in this way. 



We next worked with the eggs of Cumingia 

 which had been found to be refractory to the 

 other methods of artificial parthenogenesis. 

 We obtained an apparently perfectly normal 

 segmentation of the eggs and the formation of 

 larvse, by treating them in the following way: 

 The eggs were sensitized to the effects of 

 serum by placing them for from 2 to 4 minutes 

 into a i ilf solution of strontium chloride. 

 They were then placed for five minutes into 

 ox-serum rendered isotonic with sea water and 

 diluted with an equal part of a M/2 solution 

 of NaCl + CaCl + KCl. After having been 

 freed from all traces of serum by repeated 

 washing in a Einger solution they were trans- 

 ferred for 60 minutes into hypertonic sea water 

 (50 c.c. sea water + 8 c.c. 2i M NaCl). Con- 

 trol experiments showed that the treatment 

 with serum is the essential factor in this 

 process. 



We induced segmentation in the eggs 

 of Chcetopterus by putting them for from 

 li to 2J minutes into a mixture of 25 c.c. f M 

 strontium chloride -f 25 c.c. M/2 ISTaCl +' 

 CaClj -\- KCl, then for ten minutes into ox- 

 serum diluted with its own volume of the 

 above mentioned solution and then by putting 

 them for thirty minutes into hypertonic sea 

 water. From fixed and stained preparations 

 which Dr. Bancroft made for us, we made 

 sure that the nuclear and cell division was 

 real and not merely apparent. 



While the method needs to be perfected in 

 some details, the experiments show that it is 

 possible to induce, with the aid of foreign 

 blood serum, parthenogenetic segmentation 

 and development into larvae, in eggs which had 

 been found refractory to the other methods of 

 artificial parthenogenesis. The lysin theory of 

 fertilization is therefore more generally appli- 

 cable. Jacques Loeb, 



Hardolph Wastenets 

 The RocBaiPELLEB Institute, 

 New Yoek, 



August 12, 1912 



