72 



M. F. Plateau on the Aquatic A^-ticulata. 



that we meet with in winter in these regioas can endure ? can 

 thej remain with impunity fixed in the ice for a certain time ? 

 And, in the event of a negative answer, what is the cause of 

 the mischief observed ? 



The aquatic Articulata of our latitudes exist indefinitely in 

 water kept by means of melting ice at a temperature of 32° F. 

 As soon as we have recourse to lower temperatures, the water 

 freezes, and the question then arises to ascertain how long the 

 animals can remain completely fixed in ice at 32° F. 



All the experiments were made in winter upon the species 

 which are met with in Belgium in December and January. 

 They consisted in placing an aquatic insect or crustacean, 

 together with the bulb of a Centigrade thermometer, in a thin 

 glass tube containing a little water and surrounded by a freez- 

 ing-mixture intended to produce the complete congelation of 

 the liquid. Care was taken not to allow the temperature of 

 the ice formed ever to descend below 0° C. After the lapse 

 of a certain time the tube was taken out of the freezing-mix- 

 ture and immersed in water of the temperature of the room, 

 when, as soon as a commencement of fusion permitted, the 

 lump of ice was extracted from the tube and put directly into 

 water, in order to hasten the disengagement of the animal. 



The analysis of the results which I have obtained shows 

 that the time during which the aquatic Articulata may be fixed 

 in ice without perishing is excessively short, the longest resis- 

 tance not having reached half an hour. The following num- 

 bers will give an idea of the rapidity with which death ensues 

 under these circumstances : — 



I have endeavoured, by means of special experiments, to 

 explain the cause of the rapid death of animals imprisoned in 

 ice at 0° C. ; but although these may, perhaps, be of a nature 



