CHRONIZOOSPORES OF HYDRODICTYON, 59 



Their contents increase in like proportion, whilst the granular 

 portion forms numerous amylon-cells, and assumes all the 

 character of the endochrome of the ordinary cells. 



Under favorable circumstances, at the end of a few days 

 the same phenomena may be observed within these polyhedral 

 cells which M. A. Braun has so well described as preluding 

 the formation of new networks. As a last result of this vital 

 effort, the endochrome attached to the cell-walls divides 

 into a multitude of distinct zoospores, which remain at first 

 fixed where they were formed, giving to the membrane that 

 supports them a reticulated appearance (fig. 18). 



When these zoospores begin to move, the thick membrane 

 which forms the generative utricle undergoes a sort of redu- 

 plication, its external layers are broken up and dispersed like 

 the shreds of a cuticle ; and the internal layers, of a gelati- 

 nous nature, are laid bare (figs. 19 and 20). At the same 

 time the young zoospores, whose activity scarcely lasts from 

 twenty to forty minutes, unite into a little network, which 

 sometimes consists merely of a few meshes forming a 

 single layer, but more often, especially in those large poly- 

 hedrons rich in endochrome, in which a great many zoo- 

 spores are produced, it forms a completely closed sac, like the 

 well-known network of Hijdrodictyon. 



In the same manner as the young networks, engendered 

 within the cells of the adult Hydrodictyon are enclosed in a 

 gelatinous envelope, evidently derived from the internal 

 layers of the parent-cell, so also are those produced in the 

 polyhedral utricles. They grow without any increase in the 

 number, but simply by the augmentation in volume of the 

 joints, and at last each of them, in the course of its further 

 development, bursts its mucous envelope, which disappears 

 entirely. 



The networks arising from the polyhedrons differ in no 

 essential respect from the young Hydrodictyon ; but, whilst 

 the latter consist commonly of many thousand cells, some- 

 times of thii'ty thousand, according to M. Braun, the former 

 rarely present more than two or three hundred. 



{To he continued^ 



