EXPERIMENTS IN THE KEEPING OF PLANKTON ANIMALS. 559 



The Experiments. 



For brevity, the results of the experiments Avill be considered in a 

 summarised form, the experiments being grouped together according to 

 the vessels in which they were carried out. The recorded averages and 

 maxima refer to the life period in days occurring among animals of the 

 several experiments in each group. The experiments carried out in 

 Positions A and B, in all of which the vessels were exposed to the in- 

 fluence of air temperature changes, will first be dealt with. Later, the 

 experiments in Position C, in all of which the vessels were submerged, 

 will be treated in the same manner, and the results of these will then be 

 compared with those in Positions A and B. The dates given are those 

 on which the different experiments were started. 



Positions A and B. 



In the experiments to be referred to, all but those made in 11-litre bell- 

 jars were carried out in Position A, The results are marked with great 

 irregularity. In certain exceptional cases, specimens lived for a con- 

 siderable period, but the averages are almost consistently low, and it is 

 evident that some factor entered into all the experiments which rendered 

 the conditions unsuitable and in most cases quite intolerable. In some 

 preliminary experiments in tank water, to which no Nitzschia or other 

 food was added, rather lower averages occurred, but in other respects 

 no distinct advantage was traceable to the kind of water used, which 

 included Berkefeld, Berkefeld diluted, the same with Miquel-Allen 

 solution in full proportions, " outside " water untreated, and the same 

 sterilised. Some species appear to be more delicate than others, and 

 among nauplii the mortality was exceptionally high. The different forms 

 will, therefore, be considered separately. 



Zoaeae. These should perhaps be viewed in a different category from 

 the rest, since it is doubtful whether a suitable food was found for them, 

 though Nitzschia, Chlorodendron, and Ciliate cultures were tried. In a 

 total number of 18 experiments with from 4 to 11 specimens, in finger- 

 bowls (June 11th to July 30th), the average time of survival was from 

 5 to 7 days, the maximum ranging from 11 to 16 days. 



Calanus finmarchicus. In finger-bowls, 5 experiments comprising 

 from 5 to 12 specimens (June 19th to August 7th) showed in Berkefeld, 

 Berkefeld diluted, and Berkefeld diluted plus ]\Iiquel-Allen solution, 

 comparatively little difference of average, 11 to 14 days, from that of 

 3 experiments in tank water (10 days), to which no Nitzschia or other 



