548 THE NATURAL HISTORY OF 



duce, instead of two, eight secondary cells, so, on the 

 other hand, may the motile encysted zoospore, which nor- 

 mally produces fom* secondary cells, divide into only two. 

 (Figs. 22, 23, 35.) 



It appears that both longitudinal and transverse divi- 

 sion of the primordial cell may take place ; but that the 

 vibratile cilia of the parent-cell retain almost to the last 

 moment their function and their motion, after the pri- 

 mordial cell enclosed by it has long been detached as a 

 whole, and become transformed into the independent 

 secondary cells, (fig. 38.) 



The individuals of the secondary generation, when the 

 encysted parent-cell divides into two, are for the most 

 part equivalent to their parent; but should the latter 

 divide into more than two, its progeny then is very dis- 

 similar to it. For the encysted zoospores may also 

 divide into a generation of eight, sixteen, thirty-two, 

 according as the primordial cell has been partitionec' 

 into eight, sixteen, or thirty-two portions, which become 

 organised into as many independent primordial cells. 

 The individuals of the secondary generation are of 

 course smaller, in proportion to the greater number of 

 parts into which the primordial parent-cell was sub- 

 divided, and they are also the more dissimilar to it in 

 proportion to the less quantity of its substance that they 

 may contain. 



These minute zoospores, however they may originate, 

 are always true primordial cells, and, under unfavorable 

 circumstances, perish as such. What becomes of them 

 under other circumstances is not very easy to deter- 

 mine. It is certain, however, that they can pass into the 

 still form, assuming a globular shape, losing the vibratile 

 cilia, and secreting a ligneous membrane. They some- 

 times undergo this change while still within the parent- 

 cell. They thus constitute a mulberry-like mass, which 

 gradually increases in size as the individual cells grow 

 (Fig. 40). They are also, after their liberation from 

 the mother-cell, sometimes seen to form an enveloping 



