12 CHAPTER II. 



that a temperature of 80 to 90 C. will generally be amply 

 sufficient^ and that very frequently it will not be necessary to 

 go beyond 60 C. An exposure to heat for a few seconds will 

 generally suffice. 



Small objects (Protozoa, Hydroids, Bryozoa) may be brought into a drop 

 of water in a watch-glass or cm a slide, and heated over the flame of a spirit 

 lamp. For large objects, the water or other liquid employed as the vehicle 

 of the heat may be heated beforehand and the animals thrown into it. 



As soon as it is supposed that the protoplasm of the tissues is coagulated 

 throughout, the animals should be brought into alcohol (30 to 70 per cent, 

 alcohol) (if water be employed as the heating agent). 



An excellent plan for preparing many marine animals is to kill them in 

 hot fresh water. Some of the larger Nemertians are better preserved by 

 this method than by any other with which I am acquainted. 



12. Slowly Contracting Animals. Animals that contract 

 but slowly, such as Alcyonium and Veretillum, and some 

 Tunicates, such as Pyrosoma, are very well killed by 

 throwing them into some very quickly acting fixing liquid, 

 either used hot or cold. Glacial or very strong acetic acid 

 (VAN BEN EDEN'S method) is an excellent reagent for this 

 purpose ; it may be used, for example, with some Medusae. 

 After an immersion of a few seconds or a few minutes, 

 according to the size of the animals, they should be brought 

 into alcohol of at least 50 per cent, strength. See lc Acetic 

 acid " and ' * Tunicata." Lemon juice employed in this way 

 has given me very good results with small Annelids and 

 Hirudinea. Corrosive sublimate is another excellent reagent 

 for this purpose. 



Narcotisation. 



13. The secret of narcotisation consists in adding some 

 anaesthetic substance very gradually, in very small doses, to 

 the water containing the animals, and waiting patiently for 

 it to take effect slowly. 



The Tobacco-smoke Method for Actiniae, due to Lo BIANCO (Jena 

 Zeit. Naturw., Bd. xiii, 1879, p. 467; Mitth. Zool Stat. Neapel, Bd. ix, 

 1890, p. 499), used to be practised as follows: A dish containing the 

 animals in water is covered with a bell-glass, under which passes a curved 

 glass or rubber tube, which dips into the water. Tobacco smoke is blown 

 into the water for some time through the tube, and the animals are then left 

 for some hours. More smoke is then blown in, and the animals are left over- 



