HUXLEY. — ZOOLOGY ; SUPPLEMENTARY INSTRUCTIONS. 61 



The external and internal parasites of mammals, birds, and 

 fishes should be sought for and preserved in spirit, the organs of 

 the animal from which they are obtained being carefully noted. 

 It would be interesting to know if the Arctic Canidse are liable to 

 be infested with Pentastomum, a large-sized vermiform parasite 

 which occurs in the frontal sinuses of the dog. The abdominal 

 cavity of fishes of the cod tribe and other deep-water fishes may 

 yield specimens of the worm-like Myxioid fislies, of which only 

 very few forms are at present known. 



The experience of previous voyagers shows that amphipod and 

 isopod Crustacea may be captured in great numbers by letting 

 down a piece of meat into an ice-hole ; and the exploration of the 

 contents of the stomachs of fishes, and especially of any of the 

 whalebone whales, will probably yield a harvest of pelagic Crus- 

 tacea and Molluscs. 



It is needless to remark on the importance of dredging when- 

 ever opportunity offers, and on the value of all specimens of 

 stalked Crinoids that may be obtained. The rare and singular 

 Ascidian Cheli/osoma, the test of which is covered with polygonal 

 plates, may possibly be met with, and, if so, should be carefully 

 preserved in spirit. 



One of the most interesting points to which the naturalists can 

 direct their attention, however, is the obtaining of materials for 

 the determination of the nature of the microscopic surface Fauna 

 and Flora, and the comparison of it with the sea bottom in the 

 same localities. The latter will, of course, be obtained by sound- 

 ing. The former may be secured and preserved in the manner 

 adopted by Dr. Hooker in the Antarctic expedition. This method 

 consists simply in filtering a certain quantity of sea-water, taken 

 at the surface and free from obvious impurities, through fine filter 

 paper. After a sufficient filtrate has been obtained, the square of 

 filtering paper may either be folded up with the filtrate inside, 

 the latitude and longitude being written with a dark black pencil 

 on the outside, and simply dried ; or better still, it may be put, 

 while still damp, into strong spirit. Perhaps even water, strongly 

 impregnated with creosote, might suffice to preserve such collec- 

 tions; but it will be desirable not to trust to this without first 

 trying the effect of maceration in such a fluid on the paper. 



SalpcE arc excellent collectors of surface organisms, and when- 

 ever they are met with in numbers it will be worth while to pre- 

 serve a good many for the sake of the microscopic organisms 

 contained in the alimentary canal. In the case of the larger 

 SalpcB, the end, usually coloured, which contains the stomach may 

 be cut off from a number of specimens, and preserved for the 

 same purpose. 



The stomachs of Lamelliljranchs obtained by the dredge will 

 give equally valuable information respecting the minute organisms 

 at the bottom. 



