678 STUDIES IN GENERAL PHYSIOLOGY 



The fact that the fusion of two eggs into one giant embryo 

 occurs so much more readily in Chsetopterus than in Arbacia 

 may be due to the difference in the viscosity of the two eggs. 



The formation of one giant embryo from two eggs in 

 Chsetopterus is so very interesting for the reason that the 

 Chsetopterus egg possesses a characteristic cell-lineage. We 

 must conclude from this that the cell-lineage is either a sec- 

 ondary element in the formation of the embryo or that the 

 earlier processes of differentiation in the Chsetopterus egg 

 are partly or wholly reversible (see section x). 



I have made very few experiments with CaCl 2 , but in 

 these giant embryos were formed. Eggs that had been in a 

 solution of 90 c.c. sea-water -f- 10 c.c. 5u CaCl 2 for one hour 

 gave rise to a number of giant embryos. A sure way to 

 produce giant embryos in Chsetopterus is to put the unfertil- 

 ized eggs for about one hour into a mixture of 97 c.c. sea- 

 water + 3 c.c. 2 KCL 



I have occasionally, but very rarely, found that the fertil- 

 ized eggs of Chsetopterus show agglutination in normal sea- 

 water. The same phenomenon seems to occur in the eggs of 

 Ascaris, according to Zur Strassen. 1 



Dwarf embryos are rarely found in Chsetopterus. I have 

 found them in the experiments with HC1. Perhaps the 

 existence of a membrane prevents the unfertilized eggs of 

 Chsetopterus from forming dwarf embryos as easily as the 

 unfertilized eggs of the sea-urchins. 



VII. ON DIFFERENCES BETWEEN THE ARTIFICIAL PARTHENO- 

 GENESIS OF ECHINODERMS AND CH.ETOPTERUS AND THE 

 POSSIBILITY OF A HYBRIDIZATION BETWEEN THE TWO 



It is impossible to hybridize Arbacia and Chsetopterus in 

 normal sea-water. I have tried a number of experiments 

 with negative results, as was to be expected. The negative 



i ZUR STRASSEN, loc. cit. 



