4 EMBRYOLOGY OF THE STARFISH. Part I. 



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 con- 

 taining fresh sea-water, and stirring the mixture thoroughly to insure the contact 

 between the spermaries and the eggs, will be sufficient to fecundate the latter. In 

 order to make the operation perfectly successful, some precautions are necessary : 

 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 clodded together decompose very rapidly, and endanger the safety of the eggs, 

 even when the water can be changed with the greatest facility. As soon as the 

 fecundation is fulfilled, the water in the dishes must be repeatedly 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 interval of two to four 

 hours may elapse before renewing the water. As it is extremely difficult to change 

 the water after the embryos have hatched and are swimming freely about in the jar, 

 without losing many of them, it is advisable, before they hatch, which is about ten 

 hours after the fecundation, to reduce the water to a minimum volume, and then 

 simply to add a little fresh sea-water and remove the contents of the vessel to larger 

 and larger jars. In this way the water can be maintained sufficiently pure, until the 

 young embryos have taken the habit of swimming near the surface, when it may all 

 be drawn off by means of. a siphon. A great deal of time and trouble will be saved 



