36 STRUCTURE AND LIFE-HISTORY OF VOLVOJi GLOBATOR. 



ON THE STEUCTUKE AND LIFE-PIISTOEY OF 

 VOLVOX GLOBATOR. 



BY A. W, WILLS. 



[Read befove the Society, May liith, 1880.] 



No single organism in Nature has more frequently excited 

 transient feelings of admiration or interest than Volvox globator. In 

 the household or at public displays of microscopic objects, none more 

 often elicits expressions of wonder and dehght. The exquisitely pure 

 green of its translucent spheres, their inimitable symmetry, and, above 

 all, the perfect grace of movement in a group of these plants, gliding 

 hither and thither with a methodical and stately rotatory motion, 

 passing and repassing, threading their way between one another, the 

 easy regularity of their courses never interrupted by collision, but only 

 checked for a moment when they approach too nearly, and then 

 instantly resumed ; in addition, the entire absence of any apparent 

 actuating force to account for tliis motion ; — all these things combine 

 to make Volvox an object of unsurpassed beauty and of perennial delight. 

 Indeed, the microscopist can offer no more attractive spectacle than that 

 of a group of Volvox-spheres, young and old, seen under a low power 

 of his instrument, by a well-adjusted dark back-ground illumination. 



Yet it is an undoubted fact that the details of their more intimate 

 structure are unknown, even to the majority of professed microscopists. 



Eefeeences to Plate VII. 



Fig. 1.— Mature Volvox sphere, showing daughter-spheres within, these also 



containing the enlarged gouidia, from wliifh spheres of the third 



generation are to be derived ; also showing hexagonal structure and 



connecting threads. 

 Fig. 2.— Portion of Volvox sphere treated by glycerine, after Williamson. 

 Fig. 3, — Portion of Volvox sphere after treatment with solution of aniline 



purple. 

 Fig. 4, a to e.— DevelDpment of young Volvox from selected gonidia within 



the parent ; a to e— the same seen in section. 

 Fig. 5.— Probable section of portion of living Volvox, after Williamson. 

 Fig. 6.— Volvox ruptured under pressure, and treated by aniline purple, 



showing radiating streaks of primor<iial utricle. &c. 

 Fig. 7.— Portion of cell wall, showing the pores through which the cilia 



protrude. 



Refebences to Pl.\te Vin. 



[The figures in this plate are drawn from a paper by A. W. Bennett, Popular 

 Science Review, July, 1878.] 



Fig. 1.— Monfficious Colony of Volvox. showing a, a2, Antheridia ; n3, Anthero- 



zoids; b,b2, tiynogonidia; b'i, bi, Oospheres. 

 Fig. 2.— Complete Antheridium. 

 Fig. 3.— Oosphere penetrated by Antherozoids. 

 Fig. 4.— Fertilised Oo-sphere, or Oo-spore. 

 Figs. 5, 6.— Antherozoids. 



