218 F. MARTIN DUNCAN ON 



be more widely known and experimented with now that cocaine 

 is almost unobtainable. It is slow in action, and therefore 

 rarely causes the animal to contract, and is most successful with 

 a large number of marine organisms, such as hydroids, echinoder- 

 mata, anemones, etc. The specimen to be narcotised should 

 be placed in a glass or other dish with sufhcient clean sea-water 

 to cover it to a depth of an inch, rather more for a large object 

 such as a starfish or large anemone. The surface of the water 

 is then gently strewn over with crystals of menthol, which 

 will dissolve slowly, and in about twelve to twenty-four hours, 

 according to the size and sensitiveness of the animal, plus the 

 quantity of water in the dish, the fully expanded animal will 

 be sufficiently narcotised to be transferred to a suitable killing 

 fluid, either corrosive sublimate or formaldehyde. 



With patience and watchfulness a 70 per cent, solution of 

 alcohol may be successfully employed as a narcotic for some 

 hydroids, but it must be added to the water containing the 

 organism very cautiously and slowly, only a drop at a time from 

 a fine pipette, otherwise contraction will take place. 



Weak osmic acid solutions are valuable for fixing marine 

 Protozoa. To a watch-glass full of sea-water containing the 

 Protozoa add a few drops of a | per cent, solution of osmic 

 acid and gently stir. The organisms are then allowed to settle, 

 passed into several changes of water, stained, and mounted. 



Formalin, properly used, is undoubtedly one of the most 

 valuable preserving fluids for a large number of marine organisms. 

 It can be used with filtered sea-water, and has such powerful 

 antiseptic qualities that quite weak solutions can be employed 

 for preserving delicate structures, nor does it generally produce 

 any serious shrinkage of the tissues. It has one drawback, 

 however, and that is that it completely destroys certain kinds of 

 calcareous structures ; therefore it should never be used as a 

 preservative fluid for larval or adult forms of echinoderms or 

 calcareous Sponges. Unfortunately considerable confusion exists 

 as to the actual strength of solutions, owing to the indiscriminate 

 use of the terms formaldehyde and formalin by many authors. 

 10 per cent, formalin and 10 per cent, formaldehyde are by no 

 means one and the same thing, for the latter is two and a half 

 times the stronger. Commercial formalin contains a definite 

 c^uantity of gaseous formaldehyde, which is generally stated on 



