186 . CYCLES OF REPRODUCTION. PART 11. 



reproduce a facsimile of the parent plant as buds do, or 

 they may acquire a cellulose coat, undergo the trans- 

 formations and change of colour mentioned, and sink to 

 the bottom of the water as red winter spores. 



Under certain circumstances which do not seem to 

 be perfectly known, it happens that during the forma- 

 tion of some of the zoospores the green matter is 

 gradually changed into a red oily substance ; they lose 

 their cilia, acquire by secretion their cell-walls and a 

 mucous envelope, and float on the water as winter spores. 

 Should they be left dry, they may remain in that state 

 for an indefinite length of time without losing their 

 vitality, and as they are extremely small, they are 

 carried by currents of air into the atmosphere, from 

 whence they are brought down in the rain, and having 

 fallen occasionally in places where they were never 

 seen before, have given rise to the idea of spontaneous 

 generation. 



Many cycles may be accomplished from the still cell 

 to the zoospores, and back again, producing numerous 

 generations from the same plant before it returns to the 

 red thick- walled cell, which may again be dormant for 

 an unlimited time. These cycles, however, do not finish 

 the history of the plant, for there can be little doubt 

 that, in some stage of its existence, a conjugation of 

 two cells occurs, as in the Palmoglcea. 



Sometimes when the division of the endochrome of 

 the spore of the Protococcus is successively divided into 

 sixteen parts, or even sooner, the new cells thus pro- 

 duced get two long cilia, as in fig. 7 H, and are 

 liberated before they acquire their cellulose coat. This 

 motile primordial cell soon acquires a bag-like invest- 

 ment (fig. 7 i, K, L,) of cellulose, through which the 

 cilia pass, and thread-like extensions of the protoplasm 

 are not unfrequently seen to radiate from the primordial 

 cell to the surrounding bag, as in fig. 7 I, showing that 



