Sorbv : On Ihc Preservation of jMariiic A)iinia/s. 439 



On the whole, the more I have studied tlic preservation of 

 the natural colour of animals, the more complicated it seems to 

 become. It is really a very special branch of chemistry, and 

 I often feel that so much depends on what may seem a trifle, 

 that a very simple thing may at any time chang^e failure into 

 perfect success. Thoug^h very much remains to be learned, yet 

 in my collection I have many specimens showing- the natural 

 beautiful colours and looking- as when alive, which have been 

 kept for some years, whereas similar specimens preserved in the 

 usual way became white and opaque in a few months, days, or 

 even hours, according- to the kind of animal or liquid used. 

 The g-lycerine must, however, be undiluted, and the animals 

 transferred to a fresh lot after they have lost their contained 

 water, since its action is often quite diff'erent when any material 

 amount of water is present. 



In concluding- this part of my subject, I ought to allude 

 to the results of experiments made with the view of killing- some 

 animals in a fully-expanded condition. In many cases the use 

 of menthol is remarkably satisfactory. Though so slightly 

 soluble in sea water it gradually stupifies and kills most animals, 

 and the chief difficulty is to know when they are really dead, so 

 that when put into diluted formalin there is no vital contraction. 

 Some Actinias and Chaetopoda are good examples of this use of 

 menthol. I have specimens of Actinoloba diantlius and Tealia 

 cnissicornis permanently preserved in formalin, as fully expanded 

 as when alive, and similar specimens in concentrated glycerine 

 retaining their natural colour. In some cases menthol is of no 

 use, since the animals contract and die contracted. In a few 

 instances freshwater is the best poison, but may cause abnormal 

 swelling by diffusing into the tissues. 



This year {1903) I have been much occupied in carrying out 

 a new method for preparing marine worms as permanent micro- 

 scopical objects, so as to show not only the larger arteries and 

 veins but all the minute capillaries, filled with their own deep 

 red blood. I had in years gone by partially succeeded in doing 

 this, by quickly drying the specimens on glass, but in most cases 

 the time required for drying was so long that many or even all 

 the vessels were lost by decomposition. The plan I have lately 

 found very successful is to get rid of the water, which amounts 

 to about I'i of the weight of the animals, by keeping them for 

 a time in a concentrated solution of lump sugar. Into this the 

 water rapidly diffuses, and, if they are not kept in it more than 

 a day, there is no material back diffusion of the syrup, even 



1903 November i. 



