STRUC'TUKE OF PROTOCOCCUS 545 



becomes slacker the flagella themselves are readily distinguishable, 

 and they may be made more obvious by the addition of iodine, which, 

 however, it should be noted, always kills the plant. 



The multiplication of these ' motile ' cells may take place in 

 various modes, giving rise to a great variety of appearances. Some- 

 times they undergo a regular binary subdivision (B), whereby a pair 

 of motile cells is produced (C), each resembling its single predecessor 

 in possessing the cellulose investment, the transparent beak, and the 

 vibratile flagella, before the dissolution of the original investment. 

 Sometimes, again, the contents of the original cell undergo a seg- 

 mentation in the first instance into four divisions (D) ; which may 

 either become isolated by the dissolution of their envelope, and may 

 separate from each other in the condition of ' free primordial cells ' 

 (H), developing their cellulose investments at a future time, or 

 may acquire their cellulose investments (as in the preceding case) 

 before the solution of that of the original cell ; while sometimes, 

 even after the disappearance of this, and the formation of their own 

 independent investments, they remain attached to each other at their 

 beaked extremities, the primordial cells being connected with each 

 other by peduncular prolongations, and the whole compound body 

 having the form of a +. This quaternary segmentation appears to 

 be a more frequent mode of multiplication among the ' motile ' cells 

 than the subdivision into two, although, as we have seen, it is less 

 common in the * still ' condition. So also a primary segmentation of 

 the entire endochrome of the ' motile ' cells into eight, sixteen, or even 

 thirty-two parts, may take place (E, F), thus giving rise to as many 

 minute gonidial cells. These, when set free, and possessing active 

 powers of movement, are true zoospores (G) ; they may either develop 

 a loose cellulose investment or cyst, so as to attain the full dimensions 

 of the ordinary motile cells (I, K), or they may become clothed with 

 a dense envelope and lose their flagella, thus passing into the ' still ' 

 condition (A) ; and this last transformation may even take place 

 before they are set free from the envelope within which they were 

 produced, so that they constitute a mulberry-like mass, which fills 

 the whole cavity of the original cell, and is kept in motion by its 

 flagella 



To what extent Protococcus is an autonomous organism is still 

 doubtful, but it appears to be more or less closely connected with 

 many forms of life which have been described, not merely as dis- 

 tinct species, but as distinct genera of animalcules or of protophytes, 

 such as Ghlamydomonas, Euglena, Trachelomonas, Gyges, Gonium, 

 Pandorina, Jlotryocystis, Uvella, Syncrypta, Nonas. Astasia, Bodo, and 

 many others. Certain forms, such as the * motile ' cells I, K, L, 

 appear in a given infusion, at first exclusively and then principally ; 

 they gradually diminish, become more and more rare, and finally 

 disappear altogether, being replaced by the * still ' form. After 

 some time the number of the * motile ' cells again increases, and 

 reaches, as before, an extraordinary amount ; and this alternation 

 may be repeated several times in the course of a few weeks. The 

 process of segmentation is often accomplished with great rapidity. 

 If a number of ' motile ' cells be transferred from a larger glass into a 



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