STILL AND MOTILE CONDITIONS OF PROTOCOCCUS. 255 



of its life, we find a mass of endochrome, consisting of a color- 

 less protoplasm, through which red or green colored granules 

 are more or less uniformly diffused; on the surface of this 

 endochrome, the colorless protoplasm is condensed into a more 

 consistent layer, forming an imperfect "primordial utricle;" and 

 this is surrounded by a tolerably firm layer, which seems to con- 

 sist of cellulose or of some modification of it. Outside this (as 

 shown in Fig. 68, A), when the " still" cell is formed by a change 

 in the condition of a cell that has been previously " motile," we 

 find another envelope, which seems to be of the same nature, 

 but which is separated by the interposition of aqueous fluid; 

 this, however, may be altogether wanting. The multiplication 

 of the "still" cells by self-division takes place as in the previous 

 instance; the endochrome, enclosed in its primordial utricle, 

 first undergoing separation into two halves (as seen at B), and 

 each of these halves subsequently developing a cellulose enve- 

 lope around itself, and undergoing the same division in its turn. 

 Thus 2, 4, 8, 16 new cells are successively produced; and these 

 are sometimes set free by the complete dissolution of the enve- 

 lope of the original cell ; but they are more commonly held 

 together by its transformation into a gelatinous investment, in 

 which they remain imbedded. Sometimes the contents of the 

 primordial utricle subdivide at once into four segments (as at D), 

 of which every one forthwith acquires the characters of an inde- 

 pendent cell ; but this, although an ordinary method of multi- 

 plication among the "motile" cells, is comparatively rare in the 

 "still" condition. Sometimes, again, the cell-contents of the 

 "still" form subdivide at once into eight portions, which, being 

 of small size, and endowed with motile power, may be con- 

 sidered as "zoospores;" it is not quite clear what becomes of 

 these ; but there is reason to believe that some of them retain 

 their motile powers, and, after increasing in size, develope an 

 investing cyst, like the free primordial utricles to be presently 

 described ; that others produce a firm cellulose envelope, and 

 become "still" cells; and that others (perhaps the majority) 

 perish without any further change. 



154. When the ordinary self-division of the " still" cells into 

 two segments has been repeated four times, so as to produce 16 

 cells and sometimes at an earlier period the new cells thus 

 produced assume the "motile" condition ; being liberated before 

 the development of the cellulose envelope, and becoming fur- 

 nished with two long vibratile filaments, which appear to be 

 extensions of the primordial utricle (H). In this condition, it 

 seems obvious that the colorless protoplasm is more developed 

 relatively to the coloring matter, than it is in the "still" cells; 

 it generally accumulates in the part from which the vibratile 

 filaments or cilia proceed, so as to form a sort of transparent 

 beak (H, K, L); and it usually contains "vacuoles," occupied only 

 by clear aqueous fluid, which are sometimes so numerous as to 



