700 Methods of Microscopical Research [September, 



results. Dr. Mayer commends it very strongly, and states that 

 with eggs containing a large amount of yolk material, like those 

 of Palinurus, it gives better results than nitric, picric or picro- 

 sulphuric acid. It is not so readily removed from objects as 

 picro-sulphuric acid, and for this reason the latter acid would be 

 used wherever it gives equally good preparations. 



2. Alcohol. — In the preparation of animals or parts of animals 

 for museums or histological study, it is well known that the chief 

 difficulties are met in the process of killing. Alcohol, as com- 

 monly used for this purpose by collectors, has little more than its 

 convenience to recommend it. Dr. Mayer has called attention to 

 the following disadvantages attending its use in the case of marine 



(i) In thick-walled animals, particularly those provided with 

 chitinous envelopes, alcohol causes a more or less strong macera- 

 tion of the internal parts, which often ends in putrefaction. 



(2) In the case of smaller Crustacea, e. g., Amphipods and 

 Isopods, it gives rise to precipitates in the body-fluids, and thus 

 solders the organs together in such a manner as often to defy 

 separation even by experienced hands. 



(3) It fixes most of the salts of the water adhering to the sur- 

 face of marine animals, and thus a crust is formed which prevents 

 the penetration of the fluid to the interior. 1 



(4) This crust also prevents the action of staining fluids, except 

 aqueous solutions, by which it would be dissolved. 



Notwithstanding these drawbacks alcohol is still regarded at 

 the Naples Aquarium as an excellent fluid for killing many ani- 

 mals designed for preservation in museums or for histological 

 work. In many cases the unsatisfactory results obtained are to 

 be attributed not to the alcohol per se, but to the method of using 

 it. Most of the foregoing objections do not, as Dr. Mayer has 

 expressly stated, apply to fresh-water animals ; and Dr. Eisig in- 

 forms me that he has no better method of killing marine annelids 

 than with alcohol. Judging from the preparations which were 

 kindly shown to me, and which were all beautifully stained with 



1 Dr. Mayer first noticed this in objects stained with Kleincnberg's hematoxylin, 

 and afterwards in the use of cochineal, where a gray-green precipitate is sometimes 

 produced which renders the preparation worthless. Such results may be avoided by 



