OF THE TOLVOCmA. 525 



which he had some reason to suppose it a peculiar mode of development, 

 ranks it as only a species of Volvox, instead of elevating it to the rank of a 

 genus, and calls it Volvox Splicerosira. Dujardin also denied the distinction 

 drawn by Ehrenberg between Sj^harosira and Volvox, but did so from mis- 

 taken views ; for he re^^resented Volvox to have only a single filament, whereas 

 both this and Spluerosim have two. '' It presents the appearance," says 

 Mr. Busk {M. T. 1852, p. 33), '' of a transparent globe, set with green spots, 

 but it differs from the ordinary varieties of Volvox Glohator in two important 

 respects : 1, in the absence of any internal globules or embryos ; 2, in the 

 irregular size of the green granules lining the wall which, instead of being of 

 uniform size, are of various dimensions. The difPerent- sized granules are 

 irregularly disposed, although, in relation to the sphere itself, they, or rather 

 the centres of them, are as regularly distributed as in the three just-described 

 forms (of Volvox). AMiat is rather remarkable with respect to this form is 

 the cii'cumstance that the larger granules are not disposed over the whole 

 peripheiy of the sphere, rarely occupying more than two-thirds of it towards 

 one side." Again, he adds — '' The smaller ones appear to resemble in all 

 respects those of Volvox Glohator, and each to possess two cilia, which is im- 

 portant, if true, because the only distinction between Volvox and Sj^hcerosira 

 in Ehrenberg's classification depends upon the circumstance that in Splice- 

 rosira there is only one cilium to each zoospore, whilst there are two in 

 Volvox. 



*' My supposition that S. Volvox and V. Glohator are aUied is founded, it 

 must be owned, not upon any direct observation, but chiefly on the fact that 

 in the water in Avhich the specimens of Volvox were contained there were at 

 first none of SphcBrosira, any more than of V. aureus, and that after some 

 days both were veiy numerous. The difference I am about to describe in the 

 after- development of the ciliated zoospores is not by any means a sufiicient 

 ground upon which they should be deemed distinct species, because much 

 greater differences are known to exist in other of the lower Algae during their 

 various forms of development, without it being thence allowable to suppose that 

 they are of different species. In Volvox Splicerosira, then, as at all events it 

 may be termed, the larger green granules are in fact the ciliated zoospores in 

 a state of fui'ther progressive development. In the same specimen they wiU 

 be seen in aU states of division or segmentation, — fii^st into two, then into four, 

 and so on, till, as in the case of the embryo Volvox, the ultimate result of the 

 segmentation constitutes numerous minute ciliated cells or bodies, not, how- 

 ever, as in that case, lining the inner surface of the wall of a spherical case, 

 but forming by their aggregation a discoid body in which the separate fusi- 

 form cells are connected together at one end, and at the other are free, and 

 furnished each with a single cilium. In this stage their compoimd masses 

 become free and s^im about in the water, constituting, in fact, a species of 

 the genus Uvella, or of Syncrypta of Ehrenberg." 



Mr. Carter affirms {A.N.H. 1859, iii. p. 4) that SiDhcBrosirci is not a distinct 

 genus, but the " spermatic form " of Volvox Glohator, which he describes as 

 one phase of development of this species, wherein upwards of a hundred of 

 the gonidia, scattered over the periphery of the primary gemmae of the parent 

 globe, divide repeatedly imtil they are broken up " into 128 (?) linear ciliated 

 segments, which are ultimately arranged vertically upon the same plane, in a 

 circular tabular group, with their cilia upwards ; and when the latter are 

 sufficiently developed, the group oscillates and rotates by theii^ aid both upon 

 its long and short axis. These segments are, in fact, the spermatozoids, 

 each of which, when they separate, is obseiTed to be linear, hom-shaped, 

 and colourless anteriorly (where it is attenuated), and greenish posteriorly. 



