EXPERIMENTS IN THE KEEPING OF PLANKTON ANIMALS. 565 



In the experiment in which the loss of the specimens was attributed 

 to bacterial infection, bright carmine patches appeared colouring the 

 dead bodies of the specimens, other objects at the bottom of the vessel 

 being suffused with the same colour. Mr. Harold Drew kindly tried to 

 cultivate the Bacteria on peptone agar, but no growth was obtained. 



The circumstances of the failure of the two experiments (November 

 30th) in connection with the use of an air-supply are as follows : — 



Each experiment concerned 20 specimens. 



(No. 174.) Till the 14th day, several were seen very active, and on 

 this day from 20 to 30 nauplii were observed. On the 15th day, all the 

 nauplii and nearly all the adults were dead. On the 19th day, only one 

 of the adults remained alive, showing little movement, on the bottom of 

 the vessel. 



(No. 175.) On the 14th day, about a dozen adults and a few naupHi 

 were seen. No subsequent records were made till the 19th day, when 

 nearly all were dead. On the following day a few nauplii still survived, 

 but these died soon afterwards. 



In these two experiments the vessels had been provided with an air jet, 

 forced through the water by connection with the air-pressure system of 

 the Laboratory, during the 24 hours between the 13th and 14th days. 

 When on the 14th day the air-supply was taken off, and the vessels 

 removed from the tank for examination, they remained exposed for 

 about half an hour to the much higher air temperature of the Labora- 

 tory. The rise in the temperature of the water thus caused w^as not 

 observed, but it seems possible that the air-saturated water of the 

 vessels thus parting rapidly with air in solution, injury was caused 

 to the blood system of the animals. 



Calanus finmarchicus. In 2-litre beakers, submerged in the tank, 

 5 experiments (November 30th to January 13th) resulted, as far as the 

 observations were carried, as follows : — 



Max. Period of Life Average, 



Experinieiits. Specimens. Recorded, days. days. 



1 ... 2 ... 48 ... 35 (completed) 



1 ... T) ... 27 ... 19 „ 



1 ... 3 ... 64 ... 41 (uncompleted) 



2 ... 3,5 ... About G living on 45tli day „ 



Ova were obtained in the last two experiments, but were lost through 

 an accident. 



In 1-litre flasks submerged in a bath heated over a small bunsen flame 

 to 16°-18°, and kept by a regulating thermometer at this approximate 



