and on their Specific Differences. 7 



the elongated lip of the infusorium Trachelitis. In active 

 progression, when in the water, the cilia appear to be brought 

 forwards. 



That these spermatozoids do enter the spores as Cohn has 

 stated, may be reasonably inferred without actual demonstration; 

 for they may not only be seen to be continually dragging their 

 plastic bodies over them, and behaving in the manner stated, 

 but they never forsake them unless it be to go to another spore ; 

 added to which, the spinose development of the capsule of the 

 impregnated spores (fig. 9 c) may be observed to be proportion- 

 ally developed as the spermatozoids remaining in the cell are 

 few or numerous. Hence V. stellatus is monoecious. 



Observations. — The fact of the daughter of V. globator not 

 passing into small cells until it has arrived at more than the 

 1 -300th of an inch in diameter, while that of V. stellatus begins 

 to undergo duplicative subdivision when it is only 1 -2700th of 

 an inch in diameter (figs. 4 & 6), is sufficient alone for a specific 

 difi'erence; and when added to the diff'erence in the form of the 

 spermatozoid and the mode of fecundation, &c., there can be 

 no longer any doubt about these two Volvoces being distinct 

 species. 



Whether the daughter of V. globator is undergoing crypto- 

 division during its enlargement (fig. 4), and is thus finally pre- 

 pared at once to pass into the form of the young Volvox when 

 the time for so doing arrives, I cannot say ; but if such should 

 be the case, as I have already inferred, then we have apparently 

 a similar instance to that of the cell of Hydrodictyon, which, 

 commencing from a ciliated gonidium with one starch-cell, goes 

 on increasing in size, in the quantity of its gonimic contents, 

 and in the multiplication of the starch- cells and nuclei, until all 

 at once the mass resolves itself into a multitude of gonidia, 

 which, arranging themselves head to tail and vice versa, for the 

 most part in threes, thus pass into the form of the young 

 Water-net*. But if it be difficult to catch this point in Hydro- 

 dictyon (which is the case), where there is nothing to impede the 

 view, I do not know how it will be seen in the daughter of Vol- 

 vox globator, where the chances of meeting with it must be still 

 rarer, and the daughter always within the parent when this takes 

 place. 



Mr. Busk, in identifying the two Volvoces, observes that he 

 has seen the '^smooth and stellate globules'''' together "on 

 several occasions " (/. c. p. 32), which, had he been speaking of 

 the common form of Volvox globator, would have been confusing ; 

 but he happens to be alluding to the spore-bearing daughter of 



* For a description of this, see A. Braun's * Rejuvenescence in Nature/ 

 translated by Prof. Henfrey, pp. 222, 260, &c., Ray Soc. Pubhcations. 



