412 E. E. JUST. 



the season. Evidence for these statements is included in this 

 paper. 



In what follows it will be convenient to consider first those 

 experiments made on shed eggs during the first period of the 

 summer, and second those experiments made on both shed and 

 " ovary " eggs during the second part of the summer. 



II. 



A word concerning the method used in the experiments here 

 reported may not be amiss. Eggs used were from freshly pro- 

 cured animals whenever these were to be had. In one case ani- 

 mals were collected from the spiles of the dock opposite the labo- 

 ratory and used immediately after. Results on eggs from animals 

 kept in the laboratory in a few instances for several days, how- 

 ever, showed that such eggs may be as good as those from freshly 

 dredged animals. Each animal was thoroughly cleansed for a 

 minute or two under running tap water. The hands and fore- 

 arms of the worker were kept under a stream of tap water for 

 about one minute. After the washing under running tap water 

 the urchin was shaken dry and put under a jet of sea-water, then 

 shaken dry again. The animal was thereupon placed in a dry 

 Syracuse watch glass, aboral side clown, and its peristome carefully 

 cut with clean, sharp-pointed scissors with very slender blades. 

 Care was exercised to avoid puncturing the gonads. Frequently 

 mere puncture of the peristome was made. As soon as eggs or 

 sperm came through the genital pores as a result of the stimulus 

 of the incision the animal was removed to another dish. Controls 

 of uninseminated eggs were always run and not once was develop- 

 ment of an egg discovered. The case may be quite otherwise, 

 however, if the animals are not thoroughly washed in tap water. 

 Among eggs from such unwashed females one may find not only 

 eggs with membranes, but cleavage stages and blastulse. This is 

 particularly true of animals kept in the tanks where spawning may 

 take place. In such cases eggs caught among the female's spines 

 are fertilized where they remain until the swimming stage. 



The blood used in this work was procured in the following 

 manner: The peristome was carefully cut away and the lantern 

 gently removed. The animal was then inverted over a clean Syra- 



