4 EMBRYOLOGY OF THE STARFISH. 



those having a bluish tint being invariably females; a reddish or reddish- 

 brown color indicating a male. Among the many specimens I have had 

 occasion to open, I have thus far never found a single exception. When 

 cut open, so as to expose the genital organs, the difference between the 

 males and females is still more striking. The long grape-like clusters of 

 reproductive organs extending from the angle of the arms, on both sides 

 of the ambulacral system, to the extremity of the rays, present very 

 marked differences in the two sexes. The ovaries are bright orange, 

 while the spermaries are of a dull cream-color. At the time of spawning, 

 which is very different in the two species mentioned above, the genital 

 organs are distended to the utmost, filling completely the whole of the 

 cavity of the ray; the abactinal system itself being greatly expanded by 

 the extraordinary development of these organs. 



Artificial Fecundation. — If we take a male and female Starfish in this 

 state, and cut a portion of the genital organs into small pieces, we shall 

 find that the eggs and spermaries escape in such quantities as to render 

 turbid the water in which they are placed. Throwing these small pieces 

 of the genital organs into shallow dishes containing fresh sea-water, and 

 stirring the mixture thorovighly to insure the contact between the sper- 

 maries and the eggs, will be sufficient to fecundate the latter. In order 

 to make the operation perfectly successful, some precautions are neces- 

 sary : all the pieces of the genital organs, which are left after repeated 

 stirring, must be carefully removed ; there must not be too many eggs 

 in one dish, so that the water can have free access to them in every 

 direction. The removal of the remnants of the ovaries and spermaries 

 is very necessary, as the pieces which remain clotted together decom- 

 pose very rapidly, and endanger the safety of the eggs, even when the 

 water can be changed with the greatest facility. As soon as the fecun- 

 dation is fulfilled, the water in the dishes must be i-epeatedly changed 

 until it becomes perfectly clear, for the presence of too many spermaries, 

 rendering the water milky, prevents a favorable result. It is best only 

 to use one male and one female for the mixture in each vessel, as eggs 

 taken from many individuals lessen the chances of success. The eggs 

 sink to the bottom, so that the water can be poured off" and changed 

 without much danger of throwing them away. Immediately after the 

 mixture is made, the water should be changed three or four times in 

 succession; after that, every half-hour, until the fourth hour, when an 



