RECENT RESEARCHES INTO THE HISIOKY OF BACTERIA. 265 



rows, and united families are to be found; these latter may 

 be broken up by pressure on the cover glass, but they also 

 separate of themselves, and thus increase in number; in 

 addition to this mode of propagation, which is the more 

 common, single cells may leave the colony, and by repeated 

 divisions form a new family. 



The genus Clathrocystis, the cell-families of which are at first 

 solid, and, later on,formhollow spheres of a beautiful palegreen 

 colour, and from 0,024 — 0.5 mm. diameter, presents a still 

 more remarkable mode of division ; which was first described 

 by Henfrey,! in 1856, who saw numerous gonidia appear on 

 the surface, in a single layer, imbedded in a colourless 

 matrix ; gradually the hollow sphere takes on the appearance 

 of an irregular net, by the enlargement of fissures, arising at 

 the periphery ; the whole breaks up into fragments, which 

 grow again into hollow spheres. 



5, 6. Cohn now goes on to describe a new species of this 

 genus, to which he has given the name Clathrocystis roseo- 

 persicina, which he has found on leaves and like matter decay- 

 ing at the bottom of glass vessels, as spots of a bright peach- 

 bloom-red colour; under the microscope they appear as 

 loosely aggregated cells, rounded or oval, which are either 

 homogeneous or appear to be hollow, in which case the cavity 

 is filled with one or more dark granules. Care must be taken 

 not to confound with them other microscopic organisms, 

 which have no real genetic connection with them, although 

 of a similar colour. The first supply which led to the 

 investigation of this form was received from Dr. Kirchner, 

 who assisted Cohn in his labours ; his specimens were found 

 in a pond near Breslau, either on the surface of the water 

 or mixed up with Vaucheria, Spirogyra, &c. Material was 

 also received from Dr. Warming, of Copenhagen, and Mr. 

 Ray Lankester, of Oxford. Much of the interest, indeed, taken 

 in this plant is due to the investigations of Professor Lankes- 

 ter, published in this Journal, in October 1873;^ this paper 

 will be known to all our readers. The specimens found growing 

 on other plants were of irregular form, but with a sharply 

 marked contour, and consisted of cells united by a common 

 gelatinous membrane ; the free-swimming forms were hollow 

 spheres, of a diameter not exceeding 0'6 mm. The contents 

 were clear and fluid ; and often the spheres exhibited cracks, 

 with similar spheres and hemispheres arising from them ; the 



' 'Quart. Joum. Microsc. Science,' 1856. 



^ ' Quart. Joum. Mic. Sci-,' vol. xiii., N. S., p. 408. PI. xxji, xxiii, and 

 again vol. xvi, p. 27. 



