550 Phylum Echinodermata 



A discussion of methods of activating Asterias eggs artificially, together 

 with a bibliography of the subject, is presented by Morgan (1927). 



Bibliography 



Just, E. E. 1928. Methods for experimental embryology with special reference to 

 marine invertebrates. The Collecting Net, Woods Hole, Mass. Vol. 3. 



Lillie, Frank R. 1919. Problems of fertilization. Univ. of Chicago Press. 



Morgan, Thomas Hunt. 1927. Experimental embryology. Columbia Univ. Press. 

 Chapter 27. 



THE LABORATORY CULTURE OF THE LARVAE OF 

 ASTERIAS FORBESI 



Evert J. Larsen, U. S. Bureau of Fisheries 



THERE are three accounts in the literature of the successful labora- 

 tory culture of starfish larvae through metamorphosis. The first of 

 these is by Delage (1904) who reported the maturation of a partheno- 

 genetically developed larvae of Asterias glacialis. Gemmill (1912, 1914) 

 was able to rear Solaster endeca and Asterias rubens, the former from 

 naturally, the latter from artificially fertilized eggs. Much earlier, 

 Agassiz (1864) described a procedure for artificially fertilizing the eggs 

 of Asterias jorbesi and A. vulgaris. His method of caring for the larvae 

 was insufficient, and from his accounts none of his animals meta- 

 morphosed. 



Larvae of A. jorbesi were obtained by artificial fertilization of Asterias 

 eggs from June 5 to September 17, 1935, at the Marine Biological 

 Station of the U. S. Bureau of Fisheries at Milford, Conn. Set was ob- 

 tained from a batch begun on June 5, and later from a batch started 

 on August 18. 



The following directions include the procedures for artificially ferti- 

 lizing the eggs and rearing the larvae. They differ somewhat from those 

 of previous workers; where these differences occur the reasons for them 

 are stated. 



All the seawater used in this work must be filtered, preferably through 

 coarse filter paper because some small forms, such as copepods, feed 

 voraciously upon starfish larvae. It is not necessary to sterilize the 

 glassware or to pass the seawater through a Chamberland filter accord- 

 ing to the method used by Gemmill for Asterias rubens. It is impossible, 

 and perhaps undesirable, to prevent all bacterial contamination. The 

 water must also be fresh. The presence of adult stars is detrimental in 

 a tank from which water is obtained for culture of larvae, as has been 

 shown by experiments at the Milford Station. Other experiments indi- 

 cate that a salinity of 27-28 parts per thousand is advantageous in the 

 early larval development. Moreover, the evaporation from the culture 

 jars, which is corrected daily, does not cause a rise in salinity above the 



