[25] THE PRESERVATION OF MARINE ANIMALS HOVEY. 



of air always form in the bells, wliicb, through their tendency to float, 

 tend to change the natural shape of the bells, or, raising the whole 

 colony, flatten it at the surface of the liquid. To get rid of these bub- 

 bles it is necessary to compress the bells gently. 



(6) The genus ForsJcalia is transferred from the mixture of copper 

 sulphate and sublimate to Flemming's solution.' The animals remain 

 in this form two to six hours, according to their size, and are then 

 washed in fresh water and transferred to weak alcohol, and so on grad- 

 ually. The hardening of large colonies succeeds better in the mixture 

 of bichromate of potassium and osmic acid, where they can lie even 

 twenty-four hours without hardening too much. To free the animal 

 from the crystals which form in the tissues and render them opaque, a 

 few drops of concentrated sulphuric acid should be added to the first 

 alcohol into which the colony is put. After that, pure alcohol may be 

 used. 



For the permanent preservation of the Physophoridse, after they 

 have remained for a few days in 70 per cent alcohol in crystallizing 

 dishes for hardening, they are to be put into tubes, arranging them so 

 that the anterior end of the colony is toward the mouth of the tube, by 

 immersing the tube in the liquid and gently working the colony into it. 

 Small specimens of Agalma and Halistemma can be taken by the pos- 

 terior end with small forceps and gently forced into a tube filled with 

 70 per cent alcohol so that the bells point toward the opeuiiig. The 

 tube should be small enough to keep the colony in proper position 

 within it. it should be plugged with cotton and placed within a larger 

 tube filled with 70 per cent alcohol and closed with a cork. This double- 

 tube system j^revents movement of the liquid about the colony itself, 

 even when the outer tube is not entirely filled with alcohol. It is like- 

 wise very useful for shipment of specimens, and especially so for pur- 

 poses of demonstrations. It is recommended for all very delicate 

 animals and those with appendages which can be injured easily. 



Apolemia uvaria is killed as are the preceding species and hardened 

 with 1 per cent chromic acid, which is substituted (in the same dish) for 

 the sulphate of copper and sublimate mixture which has been drawn 

 oft' through a siphon. After twenty minutes in the acid, wash in fresh 

 water and transfer to alcohol, the change of fluids being effected by 

 means of siphons. 



Rhizophysa should be allowed to expand in a beaker with the least 

 practicable amount of water and should then be killed with hot satu- 

 rated sublimate. Wash at once and put into weak alcohol, rearranging 

 as far as possible the net tie- filaments and tentacles which have become 

 tangled during the handling. 



Physalia caravella should be permitted to expand its appendages and 

 polyps in a tall cylinder filled with clear sea water, taking care not to 

 touch the pneumatophores on account of their severe stinging action. 



' Chromic acid of 1 per cent, 25 c. c. ; osmic acid of 1 per cent, 10 c. c. ; glacial 

 acetic acid, 5 c. c, and distilled water, 00 c. c. 



