ON THE ARTIFICIAL CULTURE OF MARINE PLANKTON ORGANISMS, 467 



other hand, to which no culture was added, there was considerable 

 growth of diatoms and of a tiagellate, upon which the Plutei fed. The 

 first young Echiims were recorded in both jars on June 8th (64 clays), 

 but may have been present a few days earlier. Eventually from 30 

 to 40 metamorphosed in one jar and about 12 in the other. The 

 temperature varied from 10"5° C. to 12*5'' C. 



In the second experiment (eggs fertilized June 8th, 1908), made v/ith 

 similar water, the larvae were fed on a pure culture of Nitzschia 

 closterium, var., and six had completely metamorphosed on July 26th 

 (48 days after fertilization), two more subsequently coming through. 

 The temperature was generally 15° to 16'^ or 17° C. 



In the third experiment (eggs fertilized March 29th, 1909) aquarium 

 tank-water treated with animal charcoal and then filtered through 

 a Berkefeld filter was used. Plutei, fed with a pure culture of a small 

 flagellate (probably Cldlomonas sp.) grew satisfactorily, and eight young 

 Uchinns weve found on June 5th (68 days after fertilization), which had 

 probably metamorphosed some days earlier. Two other jars in which 

 Nitzfichiadostcrium, var., was used as food, w^ere not successful, probably 

 because the growth of diatoms became too thick towards the end of the 

 experiment. 



Ecldnus iidliariH. In the first experiment with this species animal- 

 charcoal Berkefeld water was used, each jar containing as usual 2000 c.c. 

 In one jar the Plutei, from eggs fertilized on August 27th, 1907, were 

 fed on a pure culture of Nitzsdda dostcrium, var. On October 4th, i.e. 

 thirty-eight days after fertilization, one Eddnns had just metamor- 

 phosed. On October 29th about a dozen healthy-looking Eddni were 

 climbing about the jar, and many were still in a healthy condition on 

 January 8th, 1908. Temperatures: September, 15° to 19° C, October, 

 16° dropping to 13° towards end, November, 12° to 11° C, December, 

 15" to 10° C. 



To another jar containing larva3 from the same batch a few drops of 

 fresh Plankton were added as food. The Plutei in this case fed on 

 flagellates and Nitzsdda which grew in the jar, and several metamor- 

 phosed. 



In a second experiment with eggs fertilized on September 13th, 1907, 

 the larva? were fed with JSdtzsdda dostcrium, but altliough there were a 

 few v/ell-advanced Plutei still living on January Sth, 1908, none com- 

 pleted the metamorphosis. 



. Cacumaria saricola-. A female Cacumaria, one of a number in a dish 

 contaiiiing " outside " water, laid eggs, which were fertilized, and 

 segmented on May 12th, 1906. A number of these were placed in a 



