in Eudorina elegans and Cryptoglena. 243 



green contents ; and it should also be remembered that, although 

 these contents have now no other covering distinct from the 

 protoplasm but the capsule, yet in all algal cells, whenever 

 the green contents take on a new form, such as that of a spore 

 or group of cells, a second more delicate covering is separated 

 from them, for which I have heretofore used the term " proto- 

 plasmic sac* M ; these two coverings, then, are the parental divi- 

 sion of the mass, and become caducous as the rest takes on its 

 new form and developes on its surface a cell-wall. Thus we get 

 the sixteen cells separated from their capsule, &c, and sur- 

 rounded by their proper cell-wall and the external envelope, 

 which may be a still further thickening of the former, or a new 

 secretion ; but, be this as it may, the cilia are seen outside it. 

 And at first it might be thought that they were formed before 

 either the cell-wall or envelope, so as never to have been enclosed 

 by either ; but if this were the case, the cilia of the sixteen cells, 

 which are added by duplicative division to the first stage of 

 Eudorina to form the second stage, should be inside these 

 coverings, or protrude through the original sixteen channels 

 with the other sixteen pairs of cilia. However, neither is the 

 case ; for these sixteen cells have their channels respectively as 

 well as the other sixteen cells, in which case they must have 

 been made by the sixteen new cells themselves, unless the thirty- 

 two division is formed before the pellicle, which subsequently 

 forms the cell-Wall, is supplied; and our first stage does not 

 pass into the second stage, but both forms are produced at once 

 and separately from the beginning, — a point which can only be 

 determined by following the development of the Eudorina from 

 the spore itself, and that, too, alone, since it is impossible to say 

 whether the sixteen-division groups, when previously mixed up 

 with all the other forms of Eudorina, are or are not derived direct 

 from the spore, or from the third stage of development of this 

 organism. That the sixteen-division or second stage may pass 

 direct into a similar form to the third, that is, into a form of 

 Eudorina consisting of sixteen groups of sixteen cells each, I 

 have occasionally seen ; but then this form has been globular 

 (only 30-5400ths of an inch in diameter), and not ovoid, although 

 the groups have possessed the latter form : perhaps this is the 

 spore, and the sixteen groups the young Eudorina, if not a dif- 

 ferent species. Again, the robust individuals of the sixteen- 

 division one would think to be direct from the spore, and to pass 

 into the robust individuals of the second stage or thirty-two 

 division, — while the puny, meagre individuals one would think 

 to come from the third stage, and, as before conjectured, end in 

 disintegration and death. But all this, as I have just stated, 

 * Annals, vol. i. 1858, p. 31, &c. 



