The Preservation of Contractile Marine Animals in an Expanded Condition

Extract

The importance of killing contractile animals in an expanded condition cannot be over-estimated. A glance at the immense confusion and uncertainty which prevails in several branches of tropical marine invertebrates, and in particular the Coelenterata, will give a clear picture of the value of good preservation. Killing contractile animals in an expanded condition has always offered considerable difficulty. Several methods have been recommended for different animals, but it is often very difficult to choose the appropriate one, since animals belonging to one and the same group may behave quite differently towards any method. The writer, during his work for the last three years at the Marine Biological Station of the University of Cairo at Ghardaqa in the Red Sea, has taken great pains to preserve a variety of marine invertebrates as fully expanded as possible. Some of the successful results and the methods used are therefore given here.

The commonest method for the present purpose is the use of narcotics. The most familiar of these are menthol, chloral hydrate, alcohol, magnesium sulphate and cocaine. Owing to the difficulty in obtaining cocaine it cannot be freely used for general purposes. Menthol enjoys a great reputation for narcotization which, in fact, it does not quite deserve. Although in some few cases it gave good results, yet in the majority it was quite unsatisfactory, as delicate animals begin to macerate before they are properly narcotized. It is generally applied in the crystal form and sprinkled on die surface of the water. Apparently its low solubility is responsible for a great many of its failures.