570 - L. ];. CRAWSHAY. 



the 29tli day there were seen alive in it, besides the adult Calanus, a 

 few small ones, and one or two Teniora, the latter being a species for 

 which very low averages had been obtained elsewhere. 



In the experiment carried out by Dr. Allen (p. 556), in which some 

 Calanus were kept alive for not less than about 50 days, and in which 

 two of the nauplii reached the adult stage, the flask used was kept standing 

 in the water of one of the tanks. In the case of the 2 Calanus that 

 were raised by Mr. Fuchs in an EcJmiopluteus culture, the jar containing 

 these was not submerged, but was kept standing on one of the slate 

 slabs under the tanks in the same room. Here these two specimens lived 

 for 57 days, and subsequently in Position A for another 24 days, making 

 a total period of 81 days. It is not known how far this result may 

 have been exceptional, like such examples as that in which a specimen 

 lived for 84 days in a 1-litre flask in Position A, but probably, under such 

 conditions, the temperature changes in the water of a jar of 2000 c.c. 

 would at most times be slight and gradual, and not such as seriously to 

 affect the animals. 



For the 5 experiments with Calanus in vessels submerged in the tanks 

 the average, 35 days, is very incomplete, three of the experiments 

 being uncompleted. For the 4 experiments in vessels submerged in 

 the artificially heated bath, the low mortality at the time of their 

 interruption suggested an average not lower than was indicated in the 

 others, which at the close of the observations stood at rather more 

 than double the average (17 days) obtained for the 11 experiments with 

 this species in Position A. 



As a series of preliminary experiments, the results with Pseudocalanus 

 may, on the whole, be regarded as fairly satisfactory, the small propor- 

 tion of nauplii which were brought through to the adult form being 

 probably due to minor imperfections only in the conditions, possibly 

 in the food-supply which it should not be difficult to adjust. 



The results of the experiments in Position C are not as conclusive 

 as might be wished, but their difference as a whole and in detail from 

 the others is so marked as to leave little doubt that the preservation of 

 an even temperature is of the first importance in experiments with 

 pelagic Copepoda, and probably indispensable to success with the 

 majority of pelagic plankton species. 



On Diatom Growth in the Experiments. 



In nearly all the experiments in Position C with Calanus fnmarchicus 

 considerable difficulty w^as encountered in controlling the growiih of the 



