FRESH- WATER SPONGES. 00 



Myriophillum, and Utricularia. But I have found them in very 

 unlikely places, and in places where I was confident of success I 

 was disappointed. After the student has found a few specimens, 

 he will have no difficulty in identifying them, should they come in 

 his way. 



The mounting of fresh-water sponges is attended with as few 

 difficulties as any other branch of microscopy ; the chief one 

 being to obtain the specimen perfectly transparent when mounted. 

 To accomplish this, I take a small piece of the sponge, with a few 

 statoblasts, and place it on a glass slip ; then cover the sponge 

 with pure carbolic acid in crystal, if in winter, warming it gently 

 over a lamp. If in summer, most likely the acid will be fluid. 

 If so, put a drop or two on the sponge, _and let it stand for an 

 hour, more or less, till it is quite clear. In a few minutes, how- 

 ever, it is likely to be clear enough to be able to determine the 

 species under the microscope. If some of the statoblasts fail to 

 yield to the clearing properties of the acid, they may be broken by 

 pressure, or cut with a thin knife. They will then soon clear. 

 The next process is to drain off the acid, and apply balsam and 

 the cover-glass. If it is desired to mount many slides of the 

 same species, a larger piece of sponge may be soaked in a watch- 

 glass with acid for several days. 



Some prefer to boil the sponge on the slide in a drop or two of 

 strong nitric acid, repeating the process till the desired trans- 

 parency is attained ; but, as this acid does not unite with balsam, 

 I can succeed much better with carbolic acid, which readily unites 

 with it. For reducing the sponge so as to leave nothing but the 

 free spicula, it may be put into chlorinated soda, or water of 

 Javelle, as it is sometimes called. 



The spicula can then be mounted in the same manner as 

 diatoms. For more extended remarks, the student is directed to 

 the articles of Mr. Carter, published in Annals and Mag. of Nat. 

 History^ and to the monograph of Fresh-water Sponges, by 

 Edward Potts, published by Society of Natural Sciences, Phila- 

 delphia. 



Jan. i6th, i86g. 



