564 L. R. CRAWSHAY. 



51 days later, and, soon after the close of the special experiment just 

 described, a new series was started with the vessels submerged up to the 

 neck in the same manner. An improvement in the results soon became 

 apparent, and from this time the experiments were continued under 

 these altered conditions, either in one of the tanks or in a small extem- 

 porised reservoir of water. 



In the first experiment, with 6 Temora, in a 2-litre jar of water, with 

 Chlorodendron as food, one specimen only was alive on the 19th day, and 

 this did not live for more than a few days afterwards. These Teynora, 

 however, had been left standing for 7 days previously, in a beaker in 

 Position A before the experiment was started, and the result was there- 

 fore of doubtful value. 



The other experiments related chiefly to Pseudocalanus elongatus and 

 Calanus finmarchicus. The water used was in all cases " outside " 

 water, treated with one-third Miquel- Allen solution and filtered through 

 a Berkefeld filter. In the majority of the experiments the food was 

 Nitzschia ; in a few cases Chlorodendron was used. Exact data for 

 averages are wanting, and the results can only be considered in their 

 main details. In many cases the observations were unfortunately inter- 

 rupted before the complete records had been obtained. The results may 

 be summarised as follows : — 



Pseudocalanus elongatus. In 2-litre beakers, 3 experiments, each 

 with 15 specimens (November 11th to 28th), showed on the 44th, 50th, 

 and 51st days, severally, about 23 survivors. In one of these experi- 

 ments, the water having been changed on the 44th day, four were still 

 living on the 72nd day. In another a change of water on the 51st day 

 led to bacterial infection, with fatal results to all the specimens very 

 soon afterwards. In the third, one specimen was still living on the 

 121st day. 



In an uncompleted experiment with 20 specimens (December 20th) 

 a few were still living on the 50th day. 



Two experiments (Nos. 174 and 175), which failed through injury caused 

 in connection with an air-supply, are referred to below. 



Nawplii were obtained in all the experiments with Pseudocalanus, their 

 presence and growth being observed over periods which varied from 

 40 to 63 days in the different experiments, omitting the two experiments 

 last referred to. Data concerning individual life periods are not avail- 

 able, but several were recorded as reaching the adult form and, in a few 

 cases, apparently the full growth, the age at which the adult stage was 

 reached being approximately between 35 and 40 days. 



