1884.] 



MICROSCOPICAL JOURNAL. 



131 



held fast by one trap and the tail 

 grasped by another. 



To learn something of its destruc- 

 tive powers, Mr. Simms placed 150 

 perch fry in a glass vessel containing 

 specimens of Utricularia., and at 

 the end of two days all but one or 

 two had been trapped. 



Prof. Baird thinks the discovery 

 has an important bearing on the fu- 

 ture abundance of several important 

 food fishes in our country. Twelve 

 to fifteen species of the genus are 

 found within the limits of the United 

 States, and millions of fry must be 

 annually caught in the little bladder 

 traps. 



The Utricularia occurs in abund- 

 ance in carp ponds throughout the 

 country, including the United States 

 Fish Commission ponds in Washing- 

 ton, and in some localities has been 

 introduced at considerable trouble 

 and expense, as it was thought to be 

 excellent food for the carp. Prof. 

 Baird will cause every vestige of it to 

 be immediately removed from the 

 Government ponds and will warn 

 carp-culturists everywhere to exam- 

 ine their ponds and destroy any that 

 may be found there. 



The specimen received from Eng- 

 land has been placed on exhibition 

 in the Fishery Section of the Na- 

 tional Museum, where it can be seen 

 by any who are interested in the sub- 

 ject. 



The Preparation of Shellac Ce- 

 ment. 



BY THE EDITOR. 



The readers of this Journal are 

 well aware of our very strong predi- 

 lections for shellac as a cement for 

 microscopical preparations. W e 

 have usually advised, as a quick 

 method of preparing it, to dissolve 

 the shellac in alcohol and use it tur- 

 bid, as it dissolves. Only a portion 

 of shellac is soluble in cold alcohol, 

 so that a clear solution cannot be ob- 

 tained in this way. If a considerable 

 quantity of an alcoholic solution, not 



too strong, be allowed to stand un- 

 disturbed for several weeks, the un- 

 dissolved portion will subside some- 

 what, leaving a clear stratum above, 

 which may be carefully drawn oft'and 

 used. This method of obtaining a 

 clear solution of shellac is by no 

 means satisfactory, and, as it is not 

 always possible to purchase it at paint- 

 shops, we give an easy method of 

 preparing an excellent clear solution 

 of shellac. We have used a cement 

 made in this way for years with per- 

 fect satisfaction, and quite recently 

 prepared a new supply, having been 

 reduced to the necessity of using the 

 turbid solution for some time past, 

 which, although quite as efiective as 

 a cement, is not so pleasant to work 

 with. 



To prepare the cement, obtain from 

 a paint-shop a quantity of shellac 

 spirit-varnish, or prepare it by dis- 

 solving common shellac in alcohol. 

 It is well to use five or six ounces of 

 the varnish, as there will be consider- 

 able shrinkage in volume during the 

 process. Place the varnish in a bottle, 

 which it should not more than two- 

 thirds fill, and add to it about one- 

 quarter of its volume of naphtha or 

 ' petroleum spirit.' In our recent 

 operations we used gasoline, which 

 happened to be at hand, with satis- 

 factory results. Put in the cork and 

 shake well, to thoroughly mix the two 

 liquids. Let the mixture stand a few 

 minutes and shake it again, repeating 

 the operation two or three times. 

 Then let the bottle stand undisturbed 

 for twelve hours, or as much longer 

 as convenient. The naphtha will be 

 found in a layer above the shellac 

 containing the flocculent matter, 

 which, being insoluble in cold alco- 

 hol, renders the ordinary solutions of 

 shellac turbid, while the alcoholic so- 

 lution beneath will be perfectly clear. 

 By means of a syphon, extemporized 

 of a rubber or glass tube, the clear 

 shellac may be drawn oft' from be- 

 neath the naphtha. 



The solution thus obtained will be 

 too thin for microscopical use. It 



