EXPERIMENTS IN THE KEEPING OF PLANKTON ANIMALS. 561 



with little doubt accountable for the mortality of specimens, even in 

 so large a volume of water. 



Anomalocera Patersoni. In finger-bowls, 2 experiments with 6 and 

 3 specimens, were made in tank water only, to which no Nitzschia or 

 other food was added (June 10th). These 9 specimens showed an aver- 

 age of 2 days only, the maximum being 4 days. 



Acartia sp. In a 1-litre flask, a single experiment with 6 specimens 

 in sterilised " outside " water (September 18th) showed the high maxi- 

 nmm of 100 days, the average being about 60 days. This was the only 

 experiment carried out in Position A in which nauplii were certainly 

 produced, a few of these being observed continuously from the 30th 

 to the 73rd days. The number of nauplii produced, and their individual 

 life periods are uncertain. No more than four were recorded at any one 

 time. Some showed distinct growth, but none reached an advanced 

 stage. As it has been stated, 7 Temora which were included with these 

 Acartia, all died within about 17 days, and it would seem on the evidence 

 of this single experiment that the species (probably A. Clausi) is more 

 hardy than Calanus or Temora. The experiment lasted till December 

 27th. 



Nawplii (chiefly Balanus, Temora, and Calanus). In finger-bowls, 

 3 experiments with from 15 to 20 specimens in Berkefeld water (July 

 11th) showed a maximum of 4 days ; in 3 experiments, with from 20 to 

 100 specimens, in Berkefeld diluted (July 19th to 30th), the maximum 

 was about 15 days ; in 2 experiments, each with 20 specimens, in Berke- 

 feld diluted, plus Miquel-Allen solution (August 8th), the maximum was 

 about 12 days. The average for all these experiments probably did 

 not exceed 2 days. On the other hand, as it has been shown, among the 

 Acartia nauplii hatched from eggs laid in the vessel, some appear to have 

 lived for a considerable time though the individual life periods were 

 not known. 



Young Calanoids. In 1-litre flasks with several young forms naturally 

 contained in this bulk of " outside '' water, and with no additional 

 food included, 2 experiments (September 24th) showed a maximum 

 life period of 18 days only. 



In a bell- jar (Position B) an experiment in Berkefeld water with 

 mixed plankton including many young forms, and with some fine tow- 

 netting added as food (June 10th), showed several young forms, including 

 nauplii, alive and healthy on the 33rd day, and a few continued till the 

 42nd day. Soon after this all disappeared, the specimens apparently 



