258 SEXUAL GENERATION OF VOL VOX. 



linear body, thickened at its posterior extremity, and is furnished 

 with two long cilia, bearing a strong general resemblance to the 

 antherozoids of Chara (Fig. 159, h). These Antherozoids, escaping 

 from the sperm-cells within which they w^ere produced, diffuse 

 themselves through the cavity of the sphere, and collect about the 

 Germ-cells, which probably have not yet acquired any distinct 

 cell-wall ; so that the antherozoids can come into direct con- 

 tact with their endochrome-mass, to which they attach them- 

 selves by their prolonged rostrum or beak. In this situation they 

 seem to dissolve -away, so as to become incorporated with the 

 endochrome ; and the product of this fusion (which is obviously 

 only 'conjugation' under another form) is a reproductive globule 

 or Spore. This body speedily becomes enveloped by an internal 

 smooth membrane, and with a thicker external coat which is 

 usually beset with conical-pointed processes ; and the contained 

 Chlorophyll gives-place, as in Pahnoylcea (§ 186), to Starch and a 

 red or orange-coloured Oil. As many as forty of such Oospores* 

 have been seen by Dr. Cohn in a single sphere of Volvox, which 

 thus acquires the peculiar appearance that has been distinguished 

 by Ehrenberg by a different specific name, Volvox stellatus. Some- 

 times the Oo-spores are smooth ; and the sphere charged with such 

 is the V. aureus of Ehrenberg. That these two reputed species 

 are only different phases of the ordinary Volvox ylobator, had been 

 previously pointed-out by Mr. Gr. Busk ; but they were regarded 

 by him, not as generative products, but as ' still ' or ' winter- 

 spores.' — No observer has yet traced-out the developmental 

 history, either of the Stato-spores, or of the Oo-spores of Volvox 

 stellatus and aureus, or of the detached clusters of Sphcerosira ; 

 and these points offer themselves as problems of great interest for 

 any Microscopist whose locality offers ready means for their 

 solution.f 



* The term Oospore (egg-spore) may be conveniently used to designate 

 the reproductive cell which is the immediate product of the Sexual act 

 .or of the Conjugation which represents it. 



t The doctrine of the Vegetable nature of Volvox, which had been sug- 

 gested by Siebold, Braun, and other German Naturalists, was first 

 distinctly enunciated by Prof. Williamson, on the basis of the history of 

 its development, in the "Transactions of the Philosophical Society of 

 Manchester," Vol. ix. Subsequently Mr. G. Busk, whilst adducing 

 additional evidence of the Vegetable nature of Volvox, in his extremely 

 valuable Memoir in the " Transactions of the Microscopical Society," N.S., 

 Vol. i. (1853), p. 31, called in question some of the views of Prof. Williamson, 

 which were justified by that gentleman in his "Further Elucidations" 

 in the same Transactions. The Author has endeavoured to state the 

 facts in which both these excellent observers agree (and which he has 

 himself had the opportunity of verifying), with the interpretation that 

 seems to him most accordant with the phenomena presented by other 

 Protophytes ; and he believes that this interpretation harmonizes with 

 what is most essential in the doctrines of both, their differences having 

 been to a certain degree reconciled by their mutual admissions.— The 

 observations of Dr. Cohn on the sexuality of Volvox have beeu confirmed 

 by Mr. Carter (" Ann. of Nat. Hist.," 3rd Ser., Vol. iii. 1859, p. 1), who, 



