ZOOLOGICAL STATION IN NAPLES. 217 



and staining. The disadvantages often arising from the use of 

 these media in staining alcoholic preparations, such as the tearing 

 asunder of fragile tissues caused by the violent osmosis ; swelling, 

 the effects of which cannot always be fully obliterated by again 

 transferring to alcohol, and maceration, which is liable to result 

 where objects are left for a considerable time in the staining 

 liquid, may all be avoided by using alcoholic solutions. Objects 

 once successfully hardened may be left in such solutions for any 

 required time, and when sufficiently stained, be washed in alcohol 

 of a corresponding strength, and then passed through the higher 

 grades without being exposed to water from first to last. As a 

 rule, alcoholic dyes work quickly, and give far more satisfactory 

 results than can be obtained with other media. They penetrate 

 objects more readily, and thus give a more uniform colouring where 

 objects are immersed in toto. Even chitinous envelopes are sel- 

 dom able to prevent the action of these fluids. 



It is not, however, to be denied that non-alcoholic dyes may 

 often do excellent work, and in certain cases, even better than can 

 be otherwise obtained. In the case of the Titrbellaria, Dr. Lang 

 has found picro-carmine to be one of the best staining agents, and 

 this has been my experience with Dicyemidce. As Dr. Mayer has 

 remarked, the swelling caused by aqueous staining fluids is not 

 always an evil, but precisely what is required by some objects after 

 particular methods of treatment. 



From experiments recently made. Dr. Mayer has found that 

 dyes containing a high percentage of alcohol, stain more diffusely 

 than those of weaker grades, from which he infers that strong 

 alcohol robs, to a certain extent, the tissues of their selective 

 power, and renders them more or less equally receptive of colouring 

 matter. 



I. Kleinenberg's Haematoxylin.* — i. To a saturated solution 

 of chloride of calcium t in 70 per cent, alcohol, add a little alum 

 and filter. 



* May be used after all hardening fluids. 



\ Chloride of calcium, according to Kleinenberg, has no other use than to 

 strengthen the osmotic action between the hsematoxylin solution and the alcohol 

 contained in the tissues. As chloride of calcium and alum give a precipitate of 

 gypsum, it would probably be better to use chloride of aluminum, ' 7-"^^ 



V 



