318 WILLIAM SEIFRIZ. 



ECHINARACHNIUS. 



Microdissection work on the egg of the sand-dollar was under- 

 taken for the purpose of comparison with the behavior of the 

 plant ovum. 



The difference in structure and behavior of Fucus and Echi- 

 narachnius ova before fertilization is not great. With fertiliza- 

 tion two striking dissimilarities originate. There is in Echinar- 

 achnius an increase in viscosity of the protoplasm after fertiliza- 

 tion. The path of a needle closes very slowly. Furthermore, 

 there is very little change in the character of the egg wall. The 

 wall of the young embryo is of no greater thickness than that of 

 the ovum and but slightly more resistant. 



The Echinarachnius egg occasionally tolerates a very great 

 amount of dissection before completely deteriorating. At times, 

 the capacity for wall formation persists in a region of still liquid 

 plasma even after other regions of the egg have become an ex- 

 ceedingly viscous mass. This illustrates further the great 

 diversity in the behavior of the protoplasm of eggs existing under 

 apparently identical environments, and the marked difference 

 in physiological condition of different regions of the same cell. 



During the dissection of more than 20 eggs of the sand-dollar 

 but one instance of miscibility was observed, and this was the 

 rapid dissemination of granules due to the going into solution of 

 the matrix of a gelated, that is, a degenerating ovum. 



DISCUSSION. 



In spite of the variety of objects studied and the differences in 

 behavior of very similar material there are certain definite 

 properties which characterize all the protoplasm here observed. 



Streaming protoplasm is of a very liquid consistency. The 

 same is true of young, actively growing plasma such as that found 

 in the developing oogonium and the embryo of Fucus. The 

 increase in consistency of the Echinarachnius ovum following the 

 entrance of the sperm is not in harmony with this fact, nor is it 

 what one would expect; for the liquid condition of protoplasm 

 enables the elaborate chemical reactions of an active cell to take 

 place. In the ripe egg, awaiting fertilization, metabolism i? 

 reduced to a minimum, so that a liquid state is not needed as it 



