MICROSCOPIC ALGM AND FUNGI. 209 



dium-spores may be identical with Bodo saltans of Eliien- 

 berof. 



These ' swarm-cells ' continued to move about in the water 

 until they reach a situation suited for their further develop- 

 ment, — that is to say, until they arrived at a new Clostcrium . 

 And, what was especially remarked, they invariably attacked 

 a perfectly-healthy, hriskly -vegetating individual, in which the 

 jtjreen endochrom was in close opposition with the cell-wall. 

 Having attained to its goal, tlie spore enters into a new stage 

 of development — it becomes quiescent, affixes itself, and begins 

 to germinate ; that is to say, the cilium disappears, and the 

 spore, surrounded with a rigid membrane, assumes the aspect 

 of a spherical, colourless cell, whose opaque nucleus is still 

 distinctly recognizable, in close contact with the membrane 

 of the Closterixim. 



The ' swarm-spore ' now rapidly expands into a large 

 vesicle. The nucleus undergoes a remarkable change ; ic 

 disappears, and is replaced by a highly-refractive drop of 

 fluid, probablv oil, which at first occupies the greater part of 

 the cell ; this drop divides into two, then into sevei'al, and 

 ultimately breaks up into numerous granules or droplets. 

 When the vesicle has reached a diameter of about 1-100 '", 

 its contents are seen to be divided into two portions — a 

 darker placed on the side at whicli the vesicle is attached, and 

 a lighter at the outer periphery. The former, or dark portion, 

 is produced from the metamorphosis of the nucleus, and con- 

 sists of numerous larger or smaller granules. This darker or 

 granular part of the contents gradually increases at the expense 

 of the other, until at last the whole cell is filled uniformly 

 with it. When this has taken place, the reproduction com- 

 mences, the granular contents of the vesicle being broken up 

 into a vast number of spores, by which the parent cell is 

 completely filled, as is the case in Pilobolus and other Mu- 

 corineae. In most of the fresh-water Algje, however, the 

 development of spores takes place in the protoplasma lining 

 the wall of the cell. 



The parasitic growth thus described, belongs to the genus 

 Chytridium, instituted by A. Braun in his Work on ' Reju- 

 venescence in Nature.'* 



The most important point, however, is with respect to the 

 influence exerted by the Chytridium, in the course of its 

 development upon the Closterium. 



When the ' swarm-spore ' has reached a certain size, the 

 contents of the Closterium begin to exhibit a morbid change. 



* Translated by A. Henfrey, and pubUshed by tbe Ray Society in a 

 volume of Botanical and Physiological Memoirs, p. 185. A collection of 

 great value to the microscopical observer. 



VOL. III. P 



