PEOGRESS OF MICROSCOPICAL SCIENCE. 169 



was awarded to Professor Allman for his numerous zoological investi- 

 gations, and more especially for his work upon the Tubularian 

 Hydroids. The subject of these labours is one ujjon which few 

 persons are qualified to enter ; and the Council are impressed with 

 the delicacy of the work and the value of the scientific results. 



Trichormus Thompsoni (?) in America. — At a recent meeting of the 

 Microscopical Section of the Academy of Natural Science of Phila- 

 delphia, Dr. J. Gibbons Hunt exhibited specimens of, and made an 

 important verbal communication respecting, the curious alga which 

 polluted the reservoir of the Camden Waterworks last summer. 

 During the course of his remarks he observed : — "In July last the 

 water in the basin at Camden, New Jersey, was found to be unfit for 

 use. When drawn from the hydrants it was ofiensive to both taste and 

 smell. On examining this water with the microscoj)e, I found in it a 

 plant, belonging to the Nostocliaceae, diffused in great abundance 

 through the fluid in gelatinous masses of an opalescent or faint olive- 

 green colour. These jelly-like masses were much broken up, indeter- 

 minate in form, and enveloped innumerable spiral and brittle filaments, 

 each having from three to fifteen turns. Cells of two kinds make up 

 the filaments of this plant. Several subquadrate cells, about g oig-^th 

 of an inch in diameter, are arranged in linear series ; then, at nearly 

 regular intervals, globular cells — perhaps heterocysts — of equal size, 

 and about the same diameter as the other cells, are interposed. Both 

 kinds of cells are filled with granular contents. Owing to the ex- 

 tremely brittle character of the filaments, it was impossible to tell 

 how many spirals completed an adult plant. If placed in pure water 

 all the cells became quickly separated, and the ripest exploded like 

 miniature bombs, scattering their granules all round. This made it 

 very difiicult to preserve a specimen. By using a medium of the same 

 density as the gelatinous water, I have succeeded in preserving a slide 

 of this interesting plant, which I exhibit to the Section, quite unaltered 

 in appearance. It is possible this plant is the same that Mr. Thomp- 

 son found in Lake Ballydrain, near Belfast, Ireland, and described as 

 Trichormus Thompso7ii, in the 'Mag. Nat. Hist.,' vol. v., 1837, It is 

 characteristic of the Nostochaceae to increase with great rapidity under 

 peculiar conditions. During June of this year little or no rain fell on 

 the Camden basin for nearly thirty consecutive days, and the sun 

 shone with almost unobstructed power on the still surface of the 

 water. I venture to mention the subject at this meeting, because I 

 am not aware that the plant has been found before in this country, and 

 there are no correct figures of it in the books." 



Effect of Polarized Light on the Body of the Medusce, and the Crystal- 

 line Lens. — Professor J. Clerk Maxwell, in a paper before the Eoyal 

 Society, toward the end of December last, says : — " The body of a sea- 

 nettle has all the apjjearance of a transparent jelly ; and at one time I 

 thought that the spontaneous contractions of the living animal might 

 be rendered visible by means of polarized light transmitted through 

 its body. But I found that even a very considerable pressure applied 

 to the sides of the sea-nettle produced no effect on polarized light, and 

 I thus found, what I might have learned by dissection, that the sea- 



