95 



contents of the stomachs of Holothuriee, mollusks, and fish, will 

 have to undergo a peculiar process similar to that recommended 

 for guano, though, in some cases, boiling in nitric acid alone will 

 be found sufficient. I would here mention, that the process used 

 in England for cleaning guano, of boiling in chlorohydric acid, 

 carbonate of soda, and nitric acid successively, I have not found 

 to succeed, and that described by me in the London Microscopical 

 Journal is the only one that I have found to approach perfection. 



For the purpose of collecting Diatoms, it will be found conven- 

 ient to be supplied with appropriate apparatus. A tin sandwich- 

 box is an excellent reservoir for the bottles. These may be of 

 about the capacity of two ounces, which is the size I have 

 found the most convenient, and the box should hold ten or a 

 dozen of them. Sometimes it will be found convenient to be 

 provided with a few small vials, of about a drachm capacity, for 

 the purpose of holding portions of scarce gatherings. A walking- 

 stick with a ferule attached, made to receive some contrivance for 

 holding bottles, will often be found necessary. Such a one is 

 described by the present writer in Vol. V. of the London Micro- 

 scopical Journal. I have used a similar one for nearly five years, 

 and it is in as good order as when first made. Smith * and Don- 

 kin t have given some hints on collecting Diatomacete which the 

 reader will find useful. Certain species affect certain seasons, so 

 that in the same locality, at different seasons, totally different spe- 

 cies will be found. A complete knowledge of the seasons in 

 which the different species flourish is much wanted, and the stu- 

 dent will do well to pay attention to this branch of the science. 



When the gatherings are taken home, they may be turned out 

 into saucers and placed in the sun ; in this way the living Dia- 

 toms will be separated from the dead ones, the former floating on 

 the surface and approaching the light. Many of the gatherings, 

 no doubt, will be found useless, either from being mixed with 

 mud and sand, or from the mixed quality of the species con- 

 tained, and had better at once be rejected, as, unless they be 

 wanted to illustrate locality, (an almost endless task,) it will be 

 found extremely difficult to clean them in a proper w^ay, so as to 

 show satisfactorily the species they contain. Some collectors 

 examine the gatherings on the ground by means of some such 

 * Synopsis. t Mic. Soc. Trans. Vol. VI. p. 12. 



