CHAPTER XXXVI. 523 



BUJOR (Arch. Zool. exper., ix, 1901, p. 50) kills Veretillum in sea 

 water containing 10 per cent, each of formol and ether, and after a 

 minute passes into 2 per cent, solution of formol in sea water. 



985. Hydroidea in General. Directly the tow-net comes on board, 

 the Plankton must be poured into a glass jar and jelly fishes at once 

 picked out by means of a lifter or pipette, and placed in another very 

 clean jar of sea water. Leave in this jar for half an hour to allow 

 organisms to recover from shock. Note that the slightest trace of 

 chemicals in the jar will prevent their expanding. The secret of 

 successful preservation depends on keeping the animals in motion 

 while you pour in the fixer. First stir the organisms very slowly and 

 gently, and when all are in motion begin to pour the formalin slowly 

 down the side of the vessel. About 10 c.c. of 10 per cent, formalin 

 should go to 100 c.c. of sea water, but better more than this quantity. 

 Keep stirring for at least two minutes after addition of fixer. Leave 

 for a few hours and then transfer to 5 per cent, formalin ; finally 

 store in 10 per cent. To obtain medusae in a nice state of expansion it 

 is necessary to use an anaesthetic (see especially 15). Hydrochloride 

 of cocaine is possibly the best ; use a 1 or 2 per cent, solution. Place 

 the medusae in a small glass vessel with just enough sea water to 

 allow them to swim. After they have expanded add a little cocaine 

 (3 c.c. of 1 per cent, solution for every 100 c.c. of sea water). If the 

 medusae at the end of ten to fifteen minutes do not contract when 

 touched with a glass rod no more cocaine is needed ; if they are still 

 active add more narcotiser and stir ; an over-dose will cause prolonged 

 contraction. After ansesthetisation add the formalin and keep 

 stirring, and continue for a minute, or longer. Do not leave speci- 

 mens in solutions of cocaine longer than necessary. (ALLEN and 

 BROWNE in Science of the Sea. London. John Murray. 1912.) 



For further description of narcotisation methods see 15 et seq. 



For killing by heat see 13. 



Fixation. In general polyps may be very well killed in saturated 

 sublimate solution, in which they should be plunged for an instant 

 merely, and be brought into alcohol. The solution should be employed 

 cold in general for Gymnoblastea, hot for most Calyptoblastea. 



Ether attentively administered gives good results with Campanu- 

 laridaa. Hydra is very easily killed by a drop of osmic acid on a slide. 



For the methylen blue intra vitam method, see Chapter XVI ; also 

 HADZI, Arb. Zool Imt. Wien, xvii, 1909, p. 225. 



986. Medusae : Fixation. For narcotisation see 17 and above. 

 Trachymedusas and Acalephae may be fixed in the usual way in 



