246 ERNEST E. JUST. 







ment in both went on at the same rate and in prrlVrtly normal 

 fashion. I concluded, therefore, that it was not necessary to 

 wash the eggs. Also, I found later that the eggs \\ere often too 

 greatly crowded and that it was hard to make counts unless the 

 eggs were in a single layer. A trial made with very few eggs 

 unwashed in four watch glasses gave the following result (actual 

 numbers are given) : 



FIRST CLEAVAGE PLANE. 



Through Not Through 



Number. Entrance Point. Entrance Point. 



1 8 2 



2 16 4 



3 10 I 



4 12 3 



To what extent the eggs might rotate in the jelly was yet to be 

 determined. It was absolutely necessary that the relation of the 

 indicator and the sperm entrance-point remain constant; other- 

 wise, the indicator would prove a very pretty but useless phe- 

 nomenon. Could it be possible for two spermatozoa to reach the 

 egg and the indicator to form along one sperm and not the other? 

 How would such an egg cleave? These points were next to be 

 determined. 



I found, first, that the position of the indicator could be altered 

 through tilting the watch glass, for the eggs would rotate in the 

 jelly especially when they lay on the side. I found later that 

 the eggs are most liable to rotation after the sperm has dis- 

 appeared. This might easily prove a serious source of error. 

 Secondly, I demonstrated in several experiments that polyspermic 

 eggs are not apt to cleave. (Professor Lillie has obtained the 

 same results.) But with fairly dilute sperm and sea water, 

 polyspermy, which merely cuts down the number of cleaving 

 eggs, may be avoided. 



In this connection it will be interesting to note the results 

 obtained with old eggs and sperm. On July 30 eggs from a 

 female captured in the evening of July 28 were used with fresh 

 sperm of a male captured in the evening of July 29. These eggs 

 proved very susceptible to polyspermy. This proved true in 

 other trials. These eggs if they segmented at all showed sixty 

 per cent, of first cleavages through the entrance-point of the 



