422 ON THE ARTIFICIAL CULTURE OF MARINE PLANKTON ORGANISMS. 



PAGE 



Calanus finmarchicus ...... 470 



Echinus hybrid ....... 470 



Saccnlina carcini ...... 470 



Suiumary of jAIethod for Rearing Larv£e .... 471 



Bibliography ........ 472 



Introduction. The observations to be recorded in tliis Paper were 

 commenced in March, 1905. They originated in an attempt to find a 

 general method for rearing marine larval forms. Several investigators 

 liad previously succeeded in rearing Echinoderms, Molluscs, and Poly- 

 chfetes from artificially fertilized eggs under laboratory conditions, 

 but the process was generally difficult and the results more or less 

 uncertain. The most promising method seemed to be that adopted by 

 Caswell Grave (26), who was able to rear his larvae by feeding them 

 on diatoms. Grave obtained his diatoms by placing sand, collected 

 from the sea bottom, in aquaria and using such diatoms as developed 

 from this material. All the methods, however, suffered from the 

 uncertainty of not knowing what organisms were introduced into the 

 aquaria in which the larvse were to be reared, either in the original 

 sea-water or along with the food-supply. 



It appeared, therefore, at an early stage of the work, worth while 

 to make an attempt to carry out rearing experiments on a more 

 definite and precise plan, to endeavour, in fact, to introduce the larvae 

 to be reared into sterile sea-water, and to feed them with pure cultures 

 of a suitable food. This was the ideal to be aimed at. As a matter 

 of fact, it has seldom, if ever, been attained in practice ; nevertheless 

 a considerable measure of success has been achieved by working upon 

 these lines, and during the course of the work innumerable problems 

 relating to the physical conditions under which plankton organisms can 

 best flourish have presented themselves. Some account of the experi- 

 ments made may be of interest to other workers, although many of 

 the problems raised are not yet solved, notwithstanding the fact that 

 some 1500 cultural experiments have been under observation. It is 

 rather with a view of stimulating other work upon similar lines, tlian 

 of bringing forward conclusive results, that this paper is being 

 published. 



In the summer of 1907, Mr. E. W. Nelson became associated with 

 the investigation, and since that date the experimental work has been 

 carried out by him. The discussions in this paper of a more chemical 

 character, particularly the section on alkalinity, are almost entirely the 

 work of Mr. Nelson, and we have both had throughout the advantage 

 of the constant advice and help of Mr. D. J. Matthews on all such 

 matters. 



