NO. 19.] ECHINODERMS OF CONNECTICUT. 49 



The sexual glands vary greatly in size according to the de- 

 gree of maturity of the sexual products. They are voluminous, 

 as shown on Plate V, and occupy, when mature, much of the 

 space within the body walls. The number of eggs produced by 

 a single individual in one year varies with the size of the animal, 

 and is also largely dependent upon the previous food supply. 



The genital organs develop in intimate relation with the 

 tissues adjacent to the madreporic canal. When fully formed they 

 consist of five pairs of voluminous feather-like bodies situated 

 in the interradial spaces of the body, and extending freely 

 into the arms, as shown in Plate V. Each gland opens to 

 the exterior by a minute pore on the aboral surface near the 

 base of the corresponding side of an arm. 



When the sexual products are fully ripe, the eggs of the 

 female pass out of the genital pores and float about in the water 

 or sink slowly to the bottom. 



The males at the same season discharge from similar open- 

 ings milky clouds containing millions of minute sperm cells. 

 Each of these sperm cells is provided with a vibratile tail, by 

 means of which it swims about in the water. Whenever one 

 of these sperm cells comes in contact with an egg recently 

 discharged from the female, it bores its way into the substance 

 of the egg, and fertilization results. Only a single sperm cell 

 normally enters an egg; if others approach, their entrance into 

 the egg is usually inhibited. If more than one actually succeeds 

 in penetrating the egg substance, abnormal development occurs. 

 Such eggs as are not fertilized within a short time after being 

 deposited perish. 



After fertilization a series of internal changes occurs re- 

 sulting in the fusion of the nuclei of egg and sperm. The 

 processes of cleavage and embryonic development then ensue, 

 as described in the following chapter. 



The season at which the sexual products are matured in 

 Long Island Sound varies considerably with different individuals. 

 When examined in the fall the sexual glands of all the small 

 individuals and of many of the larger specimens are small and 

 inconspicuous. During the winter they increase in volume and 

 by early spring have attained nearly full size. Their feather-like 

 processes then extend far out into the cavities of the arms, and 

 4 



