A NOTE ON THE STRUCTURE OF THE LIVING 

 PROTOPLASM OF ECHINODERM EGGS. 1 



A. P. MATHEWS. 



From a study of the living protoplasm of several different 

 echinoderm eggs Wilson 2 came to the conclusion that the struc- 

 ture was alveolar, thus confirming Butschli. During the past 

 summer in connection with the study of the chemical basis of 

 mitosis I had occasion to repeat his observations and have been 

 led to a somewhat different conclusion. 



I examined the living eggs of Arbacia pitnctnlata and Astcrias 

 Forbcsii under slight compression, using Leitz -j 1 ., oil immersion 

 and ocular 4. 



In my opinion the phenomena one observes in the living fertil- 

 ized egg show that the structure of these eggs is not correctly 

 represented by the term alveolar. The protoplasm seemed to 

 me to consist of a perfectly clear, homogeneous matrix in which 

 no trace of structure could be seen, but which contained a vast 

 number of small granules. These granules differ somewhat in 

 size, those near the periphery of the egg being somewhat larger 

 than at the center, and throughout the egg, but particularly near 

 the surface, a great number of very minute granules or micro- 

 somes may be seen. 3 



The description of the protoplasm agrees with that given by 

 Wilson except that he regards these granules as alveoli filled 

 with fluid. That they are more correctly regarded as granules 

 in a homogeneous matrix may be shown in a variety of ways. 



For example, the granules may be isolated in sea-water if the 

 egg is first treated with sodium sulphate or sodium iodide, $/&N, 

 or even in some cases with neutral red. The granules after such 



1 From the Marine Biological Laboratory, Woods Holl. 



2 Wilson, Journal of Morphology, XV., 1899, p. 6. 



3 These observations confirm those of F. R. Lillie on the Chcetoptents egg (Lillie : 

 Personal communication) and of E. P. Lyon on Arbacia (see Lyon : -Amer. Jour, of 

 Physiol., 1906, vi). 



