Notes on new species and localities of microscopical organisms / by J.W. Bailey.

  • Jacob Whitman Bailey
Date:
1854
Catalogue details

Licence: Public Domain Mark

Credit: Notes on new species and localities of microscopical organisms / by J.W. Bailey. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    ON SOME NEW TEST OBJECTS. X. American Species of the Genus Monactinus. The genus Monactinus differs from Pediastrum of Meyen [Micrasterias of Eliren- berg), by having but one j)oint or horn, instead of two, to each of the cells com- posing the circumference. Several forms belonging to this genus occur in the sediment filtered from the Croton water in New York, and those here described appear sufficiently constant in character to rank as species. As I cannot satisfac- torily identify them with foreign species, I have ventured to give them names. 1. iTlonactinus octonariiis, B. (Plate, Fig. 3G.) Circumference composed of eight cells. Centre void. Habitat: Croton water, New York city. 2. ITfonactiiiiis duodeBiariiis, B. (Plate, Fig. 37.) Circumference with twelve cells. Centre with three cells. Habitat: Croton water, New York. XI. On some New Test Objects. 1. Much of the trouble experienced in resolving finely lined objects by oblique light, arises from the necessity for the lines to occupy certain favorable positions with regard to the light, which an unpractised observer may find it difficult to obtain. A test which shall remove this difficulty must be circular, with lines radiating in all directions, so as to require no displacement in order to get the most favorable illumination; for it is obvious that, on such a body, some portion will always be in the best possible position with regard to the light. A diatomaceous shell, Avhich has lines thus arranged, and which at the same time presents dots and lines of sufficient delicacy, is the Ilyalodiscus suhtilis, B. (Plate, Fig. 12) from Hali- fax, Nova Scotia. The largest disks are as finely marked as the Greenport Gram- maiophora, while the smallest specimens are not easier to resolve than the Oram- maiopliora subtdissima, B. from Providence, Rhode Island. It is probable that these Ilyalodisci may be found in considerable numbers on our northern coasts, and if so, they will prove admirable test objects. 2. A test object, which is even more difficult to resolve than either Amici’s test or the Providence Grammatoi)hora, is presented by what appears to be a variety of Ehrenberg’s Grammatophora stricta from Halifax. Lenses which easily resolved the two tests above mentioned, entirely failed to resolve the Halifax specimens, which only yielded to some new objectives (^ig-ths) made by Spencer. I should here state that, in the spring of 1853, I resolved the Greenport Gram- matophora unmistakably by a Ith of an inch objective made by Spencer, and sub.se- quently by a ith recently made by Powell, of London, for Dr. Vanarsdale of New York. Mr. Spencer informs me that, since the above observations were made, he has greatly improved his objectives, so that his Iths will readily resolve the Green- port Grammatophora.
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