128 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull 



REPRODUCTION AND DEVELOPMENT 



In the holothurians, as in the other groups of echinoderms, 

 the sexes are usually separate. Most species of Synapta, how- 

 ever, are hermaphroditic, the sexual glands forming both eggs 

 and spermatozoa, which mature at different periods. 



The eggs of our common species are beautifully transparent, 

 and have a very symmetrical type of cleavage, but are not so 

 easy to fertilize artificially as are those of the starfish or sea- 

 urchin. 



Although three of the species inhabiting Long Island Sound 

 are found in great abundance in certain localities, very little is 

 known regarding their development. The absence of such 

 knowledge seems the more remarkable when we consider the fact 

 that the eggs of all three species are matured in summer, when 

 the opportunities for investigating problems in marine biology 

 are most favorable. 



Grave* has been successful in rearing the free-swimming 



larvae of Cucumaria pulcherrima from the fertilized eggs. He 



has also observed the transformations to the adult form and 



has even been able to keep the young holothurians alive in the 



laboratory for two or three years. This has been accomplished 



by furnishing the animals with an abundant supply of diatoms 



and other minute organisms growing at the surface of a layer 



of sand. The method consists in introducing into the aquarium 



a small quantity of the surface sand which has been dredged from 



the ocean bottom and allowed to stand in a jar of sea water for 



several days. The surface will then be found to be covered 



with a film of diatoms. The aquarium with the larvae to be 



reared, after receiving a small quantity of this diatom culture, 



is covered and placed before a window where it will be well 



lighted but not exposed to the direct rays of the sun. The 



diatoms grow, and furnish an abundant supply of the natural 



food of the animals, and at the same time keep up a constant 



supply of oxygen. The water may be changed every few weeks 



to replace the salts used by the diatoms and echinoderms.t 



As in other groups, the eggs of the holothurians in which the 

 development is known, give rise to free-swimming embryos, which 



* Johns Hopkins Univ. Circulars, No. 5, pp. 24-27, iqo5- 



t C Grave. A Method of Rearing Marine Larvae. Science, vol. xv, pp. 579-580, 

 1902. 



