INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 321 



under control wlien suspended, and it is also difficult to get rid of the 

 moisture that is sure to be present. 



Mr. George Hind describes the following as a method which he has 

 found very successful : — Take a few pieces of wire about 12 inches 

 long, and bend them up so as to form rectangular frames. Make a 

 number of these frames and keep them in a racked box made for the 

 purpose, previously gumming them all round so that the web may 

 adhere to them. On finding a web, some portion of which it is de- 

 sired to preserve, one of the frames should be taken and put behind 

 the web and drawn towards the operator, when the web will become 

 cemented to the frame all round. With a pair of sharp scissors clip 

 away the rest of the web free from the wire, and if this be carefully 

 done it will be found that the desired portion of the web is tightly 

 stretched upon the frame, which can be placed in the racked box, and 

 kept ready to be mounted. 



In order to mount any portion of the web thus obtained, first 

 cement a thin paper (or metal) cell upon a glass slip. Then having 

 slightly gummed the cell, place one of the wire frames over it, taking 

 care to bring the portion of the web that is to be mounted exactly in 

 the centre. With the scissors remove the superfluous web, and place 

 another cell upon the first one, and a thin glass cover over all, securing 

 the cover with a little gum. 



Preparing Sponges.*— In a paper on the sponges dredged by the 

 Eev. A. M. Norman on the coast of Norway, Mr. Sollas makes the 

 following remarks, which are of general interest : — " In preparing 

 specimens for microscopical examination, 1 followed the ordinary 

 methods for obtaining the spicules in the free state ; but in cutting 

 and mounting ' sections,' I adopted the processes which have hitherto, 

 in this country at least, been confined to the examination of quite 

 soft tissues. A piece was cut from tlie sponge large enough to contain 

 a representative of each of its different tissues ; this was then soaked 

 in distilled water till its contained alcohol was as nearly as possible all 

 extracted ; it was then transferred to a strong stdution of gum, in 

 which it was allowed to stand for an hour or so ; finally it was placed 

 in the well of a freezing microtome, and frozen in the usual way. 

 From tlie frozen specimen, slices could be cut of any required thin- 

 ness, the razor, strange to say, passing through the soft tissues and 

 hard spicules with apparently equal ease. 



The slices so obtained were variously treated ; some stained and 

 some not, were mounted in glycerine of various degrees of strength ; 

 others wore treated first with absolute alcohol, then with carbolic 

 acid and turpentine and mounted in Canada balsam. ' Teasing ' was re- 

 sorted to in the case of some tissues with success, especially when it was 

 found desirable to observe the behaviour of the tissue with reagents. 

 Altogether the various methods pursued have, I believe, succeeded in 

 eliciting nearly all tlie information tliat could bo extracted from tho 

 specimens ; and tliat this is very far from being so complete as could 

 be wislied is to a great extent owing to the imperfect manner in which 



* '.Ann. luul Mag. Nat. Hist.,' v. (1S80) p. 130. 

 VOL. III. Y 



