OF THE PHYTOZOA. 163 



of which, though disappearing ultimately, indicate the continued life of the 

 parent-ceU, as in the development of the spermatozoids, long after the forma- 

 tion of her progeny. 



*' Thus the process of impregnation in Eudorina agrees closely with that 

 described by Dr. F. Cohn in Volvox ghhator, in which organism I had seen 

 some of the cells of the interior undergoing a spermatoid development exactly 

 like that above described, and also that pre\'iously figured by Mr. Busk, and 

 alluded to by him as one of ' microgonidia ; ' and therefore the moment I 

 perceived it in Eudorina, in connexion with Dr. Cohn's announcement, I felt 

 conduced that the latter was right, and that I had before me Eudorina also 

 undergoing a similar process of fecundation. 



'' So much for the spermatoid development ; let us now retiu'n to that of 

 the Eudorina in totality, concerning which there is still an interesting ques- 

 tion for our consideration, bearing on the early development of this organism, 

 which I have already stated my inability to supply, viz. how does the sixteen- 

 division of the cell in the third stage of development take place, so as to allow 

 the cilia to become external ? It will be remembered that this cell in the 

 second stage, before it passes into the sixteen -division of the third stage, con- 

 sists of its capsule or cell-Avall and the 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 coveiing is separated from them, for which I have heretofore 

 used the term ' protoplasmic sac ; ' these two coverings, then, are the parental 

 division 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 sepa- 

 rated from their capsule, &c., and surrounded by their proper cell- wall and 

 the external envelope, which may be a still further tliickenmg of the former, 

 or a new secretion ; but, be this as it may, the cilia are seen outside it. And 

 at fii'st 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 ciha 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 Avith 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 pelHcle 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 -divi- 

 sion 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 g-JJ^jths 

 of an inch in iameter), and not ovoid, although the groups have possessed 

 the latter form : perhaps this is the spore, and the sixteen groups the young 

 Eudorince, if not a different species. Again, the robust individuals of the 

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

 the robust indi\-iduals of the second stage or thirty-two-di\asion, — while the 

 puny, meagre individuals one would think to come from the third stage, and. 



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