Infusorial Parasites on Stickleback

Abstract

MR. N. H. POOLE (NATURE, vol. xxiv. p. 485) is apparently right in anticipating that he has discovered either a new habitat for Trichodina pediculis or a new representative of that infusorial genus. Although hitherto regarded as a parasite only of the fresh-water polypes, Hydra vulgaris and H. viridis, I have recently obtained specimens of the type in question living as a parasite, or rather a commensal, on the branchial appendages of the larva of the common newt, Triton cristatus. An allied, but marine species, Trichodina scorpæna, has been recently described by Prof. Ch. Robin, that infests in a similar manner the branchia of fishes belonging to the genera Trigla and Scorpæna, and a further search will no doubt reveal a yet more extensive distribution of the Urceolariidæ, including Trichodina, among the Piscine race. Mr. Poole will find full particulars of the data here referred to, together with an account and illustrations of all the forms so far relegated to this somewhat remarkable infusorial group, in Part V., p. 645 et seq., of my “Manual of the Infusoria”, just published.