196 DIATOMS IN THE STOMACHS 



or circles out of very thin talc ; cover the end of the glass slip 

 with a thin layer of gilder's whiting and gum-water ; when dry, 

 write on this with common ink, let it dry, put a very small drop 

 of Canada balsam upon it ; cover with a circle of thin talc, and 

 allow all to dry ; then clean the edges with benzole and water 

 mixed. It will not peel off or get dirty like printed labels. 



®n Diatoms in tbc Stomacbe of QbclUfieh 



an& Crustacea* 



By E. S. Courroux. 



THE text-books on the mounting of objects frequently observe 

 that diatoms are to be found in the stomachs of fish, par- 

 ticularly shell-fish, but seldom contain any statements as to 

 the practical results of such findings. A few remarks, therefore, 

 on the subject, by one who has made an attempt at investigation 

 in this direction, may not be out of place. 



The only fish to which I have had recourse at present are 

 shrimps, mussels, and cockles. From shrimps I have obtained 

 most plenteous gatherings, as also at times from mussels. Cockles 

 have given a moderate supply. The quantity yielded is, however, 

 a matter of chance, and sometimes scarcely any diatoms will be 

 found ; but more often than not, the result will fully repay the 

 operator for his trouble. 



In the case of mussels and cockles, and shell-fish of that 

 description, the stomach should be cut out and steeped, or even 

 boiled, in nitric acid until it is dissolved, and the resultant deposit 

 washed and cleaned after one of the methods recommended in the 

 text-books. A little special care, however, in the treatment of 

 shrimps' stomachs will not be thrown away. On removing the 

 shelly skin at the back of the head, the stomach will be seen as a 

 small, dark-coloured body, the size of a small pea. Its position 

 may generally be detected in the perfect shrimp from the dark 



