LARVAE OF ARBACIA PUNCTULATA 



417 



In all the previous experiments, care was taken to use the 

 germinal products as quickly as possible after extrusion, as it 

 was thought that staleness might have some effect upon size or 

 vigor of the larvae. To ascertain in how far this might be 

 true, the eggs and sperm from two individuals were kept in 

 separate vessels and from portions of these, fertiUzations were 

 made at the following times: 



Experiment 22. July 22, 1915 



a 8.45 a.m. (Immediately after extrusion) 



h 10.44 a.m 



c 11.45 a.m 



d 1.00 p.m 



e 4.00 p.m 



/■ 7.15 p.m 



72 HOURS 



84.3 

 85.1 

 83.9 

 83.8 

 84.2 

 84.7 



It may be seen from these figures that keeping the germinal 

 products for 10 hours and 30 minutes effected no reduction of 

 size. Moreover, these larvae seemed quite as vigorous as those 

 fertilized immediately after extrusion. 



In the experiment above, the eggs and sperm were kept in 

 Syracuse watch glasses and covered with very little sea-water. 

 Since the fact that they were thus in a highly concentrated 

 condition might explain the lack of effect of long standing 

 upon the vigor of the resulting individuals, another experi- 

 ment was performed, and some of the eggs and sperm placed in 

 separate vessels and covered with a considerable volume of water. 

 Other portions were kept in a concentrated condition as in the 

 previous experiment. All the eggs were mature and the sperm 

 was very active. The following fertilizations were made : (C 9 

 indicates eggs from the concentrated stock; D 9, eggs from the 

 dilute. Ccf designates concentrated and Dcf^ dilute sperm- 

 suspension.) • 



