THE CROSS FERTILIZATION OF ENUCLEATED ECHI- 

 NARACHNIUS EGGS BY ARBACIA SPERM. 



HENRY J. FRY, 

 WASHINGTON SQUARE COLLEGE, NEW YORK UNIVERSITY. 



If a pluteus can be produced when an enucleated egg of one 

 Echinoderm is activated by a sperm of another species having 

 different larval characters, information may be secured con- 

 cerning the respective roles of chromatin and cytoplasm in 

 heredity and development. 



Investigations of this problem down to 1924 have been re- 

 viewed by Morgan ('24). Boveri's early experiments ('89, '95, 

 '14) with Sphxrechinus eggs activated by Echinus sperm are 

 invalidated by uncertain enucleation, as pointed out later by 

 Boveri himself ('18). When eggs are shaken to pieces and 

 supposedly enucleated fragments are picked out, he found that 

 if they are studied in section some of them are seen to contain 

 chromatin undetectable in the living condition. Since he ob- 

 tained enucleated eggs by the shaking method, the larvae produced 

 do not yield dependable evidence due to the possible presence 

 of some maternal chromatin. Morgan ('96) working with the 

 same species attempted to activate enucleated eggs of both of 

 them with sperm of the other, but there was no development. 

 Godlewski ('06) secured four maternal gastrulae when enucleated 

 Echinus eggs were activated with Antedon sperm, but his work, 

 like Boveri's, is invalidated by the fact that the supposedly 

 enucleated eggs, obtained by the shaking method, probably 

 contained undetected maternal chromatin. 



Taylor and Tennent ('24) satisfied the requirement of un- 

 questioned enucleation by cutting eggs singly with a micro- 

 dissection apparatus. Of forty-nine enucleated eggs of Lytechinus 

 inseminated by Tripneustes sperm fifteen cleaved and one formed 

 a blastula without mesenchyme. In the reverse cross only 

 membranes were formed and there was no cleavage. They 

 note that their investigation is not conclusive since Tripneustes 

 was not in good condition. 



