524 Transactions of the Society. 



For the life-like preservation of Hydromedusse formalin is 

 invaluable. At the same time considerable care must be taken if 

 the best results are to be obtained. The method 1 have employed 

 for some time past, and which has yielded very satisfactory results, 

 as may be seen from the lantern slides and mounts shown to-night, 

 is as follows : On hauling in the tow-net, the contents of the can 

 attached to its base is poured into a wide-mouthed glass jar, and 

 the Hydromedusse at once picked out by means of pipettes and 

 placed in another glass jar filled with clear sea-water. As it is 

 most important to keep the medusffi in a healthy vigorous condition, 

 it is best to carry out this operation if possible in a shady corner 

 on deck, should it be a hot sunny day, for the little creatures are 

 very sensitive to a rise in temperature. The jar must be perfectly 

 clean, and free from any trace of chemicals. I have found in very 

 hot weather that it is a good plan to wrap several thicknesses of 

 wet flannel round the jar, and to keep the flannel moist with sea- 

 water, the evaporation helping to prevent any appreciable rise of 

 temperature. About half an hour after their removal to the jar, 

 the medus® should have recovered from the shock and he nicely 

 expanded ; should they look sickly, however, then we must at once 

 preserve them, but if in a healthy condition, then they may be left 

 for an hour or two, so that the work can be done on shore. 



Many specimens may be quite successfully preserved without 

 the use of an aneesthetic by the gradual addition of formalin to 

 the sea-water in the jar containing them, and this is the best 

 method to adopt on the boat should the medusae look at all 

 unhealthy. It is most important to keep the medusae in motion 

 during the addition of the formalin, and this is best done by 

 very gently stirring round and round with a clean glass rod. It 

 is also necessary to know roughly the amount of sea-water in the 

 jar, so that the right amount of formalin may be added — the right 

 proportion is about 10 c.cm. of the 4 p.c. formaldehyde solution to 

 every 100 c.cm. of sea-water in the jar. The formalin must be 

 added slowly, almost drop by drop, while the contents of the jar is 

 kept in motion by gentle stirring, and the motion continued for at 

 least four minutes after the last dose of formalin. The stirring is 

 most important, as it keeps the medusae off the bottom of the jar, 

 so that they will die in a fairly well-expanded condition, and it 

 also helps to produce an even distribution of the formalin. The 

 medusae may be left in the jar in which they have been killed for 

 a couple of hours, and should then be transferred to 4 p c. 

 formaldehyde solution for twenty-four hours or longer, and finally 

 mounted in cells or stored away in 10 p.c. formaldehyde. 



Some of the medusae, no matter how carefully the formalin is 

 added, will contract, and to obtain specimens nicely expanded with 

 the tentacles fully stretched out it will be necessary to use an 

 anaesthetic. For this purpose I place the medusae in a small Petri 



