OF THE PHYTOZOA. 149 



Volvociticce generally as unicellular plants; and they do not stand there 

 among the Algae altogether without intermediate conditions, as Alex. Braiin 

 has proved, especially from the long movement of the Volvocinece. 



" On the other hand, the external form, like the chemical and morphological 

 organization of the contents, the laws of motion, and the general physiological 

 phenomena, especially however the behaviour in the transition into the con- 

 dition of rest, in Chlamydococcus, agree so perfectly mtli the moving spores, 

 the transformation of which into undoubted plants has been demonstrated 

 with scientific clearness, that no unprejudiced observer can discover an 

 essential distinction. I have mentioned in my essay that Ehrenberg himself, 

 although he claims the moving condition of the forms allied to Chlamydo- 

 coccus as Infusoria, has declared the resting-stage of this, or a most closely 

 allied genus, to be an undoubted Alya ; and yet the mo\'ing Infusoria are 

 only a propagative form of the motionless Alga. Finally, I have succeeded 

 in demonstrating the membrane of the cells of Chlamydococcus, both in the 

 resting and ixirticularly in the moving stage, to consist of cellulose, and thus 

 in establishing the most important criterion of a vegetable cell we are at 

 present acquainted with — the ternary composition of the cell-membrane — 

 in the Infusorioid condition of Chlamydococcus. In fact, all the more recent 

 observers of Chlamydococcus, the number of whom is not inconsiderable, 

 have, almost without exception, agreed in recognizing in all coyiditions of the 

 development of this form, only a plant and nothing hut a plant. ^^ 



Besides the valuable sketch referred to, of the relations of Chlamydococcus, 

 Cohn has presented an elaborate memoir on this organism under the name of 

 Protococcus, in a paper translated for the Ray Society (Botanical and Physio- 

 logical Memoirs, 1853), and has subsequently extended his \iews of it and 

 its aiSnities in his essay on the development of microscopical Algce (EntwicJc. 

 d. mihr. Algen, 1854). Of these most important j)apers we shall make free 

 use in sketching the history of this genus. 



" The moving cell of Chlamydococcus is composed of two principal parts, a 

 hyaline spherical envelope, which is formed of a delicate structureless mem- 

 brane consisting of cellulose, and immediately surrounds colourless contents, 

 perhaps consisting of pure water. In the centre of the envelope occurs a 

 coloured globule, composed of the universal nitrogenous p>7'otoplasm or mucus 

 of vegetable cells, coloiu-ed red or green by chlorophyll or a carmine-red oil, 

 and containing imbedded in it numerous gramdes of protoplasm, as well as 

 one or more large chlorophyll- vesicles. This coloiu^ed globule is attenuated 

 at the upper end into a colomdess point ; from this go out two cilia, which 

 protrude into the water through two orifices in the membrane of the enve- 

 lope, and produce the movements of the whole. The inner coloured globule 

 is not bounded by any rigid membrane, but merely by a thickened layer of 

 protoplasm ; hence its contour is very changeable and passes through mani- 

 fold transformations in the course of its development. In particular it fre- 

 quently becomes elongated in all directions into colourless radiating filaments, 

 which keep the internal coloured globule suspended freely in the envelope, 

 and are afterwards retracted in the course of the development. 



'' The motionless cells of Chlamydococcus are of much simpler structure, 

 and, like all forms of Protococcus, consist simply of a tough spherical ceUiilose 

 membrane and green or red contents organized as primordial utricle. The 

 history of development shows that under certain conditions the contents of 

 the motionless cells become divided into a number of portions, which always 

 correspond to two, or a power of two, in their number, that these portions 

 become organized into special primordial utricles, and as such break through 

 the parent-cell, each developing two cilia, and by the aid of these rotating 



