ON THE Al^TIFICIAL CULTURE OF MARINE PLANKTON ORGANISMS. 469 



species. The food which gave most promise of success was the diatom 

 Nitzschia dosterium, var. Larv?e from eggs fertilized on July 20th, 

 1908, fed on this material lived until October 30th, and reached an 

 advanced stage. They did not, however, adopt the adult habit and 

 form tubes. Two larvae were also reared to an advanced stage by 

 using flagellates and, in later stages, the diatom Slxcletoncma costntum 

 as food. 



Sahcllana alvcolata. One experiment only was made with this 

 species on eggs fertilized on July 19th, 1908. The eggs were fertilized 

 in " outside " water and the larvai subsequently transferred to jars 

 containing animal-charcoal Berkefeld aquarium water. They were fed 

 on a pure culture of Nitzschia dosterium, var., and kept healthy and active 

 and developed well until nearly the end of October, wdien, simultan- 

 eously with a sudden drop in the temperature from 15° and 16° C. 

 to 12° and 9° C, they sank to the bottom of the vessel and in about 

 three days were all dead. Temperatures : — During July and August, 

 the temperature kept fairly constant at about 17° C, with a range 

 from 15° to 19'^ C. During September it was generally about 15° C, 

 and continued at about this level until the fall in the middle of 

 October. 



Ardiidoris tuherculata. A good many trials have been made to rear 

 the larvae of nudibranchiate molluscs, but up to the present not much 

 success has been achieved. The best experiment was one made with 

 larvffi of Ardiidoris tvhrrculata. A number of veligers of this species 

 hatched out on May 8th, 1908, from some spawn, which had just been 

 collected from the shore. Some of these were put in a flask containing 

 1000 c.c. of sterilized animal-charcoal water and about 1 c.c. of fine 

 plankton was added. On May 14th a few veligers were transferred 

 to another flask of sterilized animal-charcoal water and some pure 

 culture of the green alga, Pleurococcus mucosus, was added. Whereas 

 the larvae in the original flask did not live long, those provided with 

 the green alga fed well and developed for some time. A number of 

 them were active and vigorous on July 4th, i.e. 51 days after 

 liatching, and several were still swimming at the end of July. On 

 August 15th none could be seen moving, but two of those which lay 

 on the bottom, when examined with the microscope, showed no sign 

 of decomposition. The animal was retracted in the shell, but the 

 tissue looked healthy, and the eye- spots and otoliths could be 

 seen. The growth in the flask seemed to be a quite pure culture of 

 Pleurococcus. Larvae were examined again on September 14th, and 

 appeared much as in August, the tissue still showing no sign of dis- 



