8 



POLYGASTRIA. 



the family derives its name. These, which 

 may readily be procured in summer time, are 

 sufficiently large to be visible to the naked eye, 

 and when examined witli a microscope, even 

 of very humble power, present a spectacle of 

 indescribable beauty ; turning continually upon 

 their axes, and revolving majestically through the 

 drop of water that forms their space, they have 

 the appearance of so many microscopic worlds 

 (jig- 2). The parietes of these elegant spheres 

 are thin and pellucent as the walls of an air- 

 bubble; and in their interior, which is obviously 

 fluid, may at times be seen rotating on their 

 axes a second generation moving freely in the 

 interior of their parent, and only awaiting the 



Volvox Globator, much magnified. 



destruction of the original Volvox to escape 

 from their imprisonment. 



It was Ehrenberg* who first made the dis- 

 covery that these beautiful living globes were 

 not, as had until then been universally believed, 

 single animalcules producing gemmules in the 

 interior of their transparent bodies, which on 

 arriving at maturity by their escape through 

 the lacerated integument of the parent termi- 

 nated its existence, but that they formed in 

 reality the residences of numerous individuals 

 living together in a wonderful community. 

 This great observer had long remarked that the 

 Volvoces appeared to take no food, neither 

 were any of those vesicles discernible in their 

 interior which in all other races of Infusoria he 

 regards as the organs of nutrition a circum- 

 stance which, considering their very great size 

 when compared with other races, was well 

 calculated to arrest attention ; and he soon 

 found that the structure of their nutritive appa- 

 tus lies much deeper and is of a far more 

 delicate character than any one could have 

 previously anticipated. 



On attentively examining with glasses of 

 high power (1000 diameters) the minute green 

 specks which stud the transparent covering of 



* Abhandlungen der Koniglichen Academic der 

 Wissenschaften zu Berlin, Jahr 1833, p. 328. 



the Volvox, and which he had previously re- 

 garded as the bulbous roots of locomotive cilia, 

 he perceived in each corpuscle a bright red 

 point, and moreover discerned that instead of 

 its being a cilium which was appended thereto, 

 it was a whip-like moveable proboscis exactly 

 similar to that of the Monads described above ; 

 and further observation convinced him that 

 every green point was in reality a distinctly 

 organised Monad, possessing mouth, eye, sto- 

 machs, generative apparatus, and, in fact, all 

 the viscera attributed by Ehrenberg to the free 

 Monadinidae, and that the Volvox was entirely 

 made up of an association of similar individuals 

 (fig- 3). 



Fig. 3. 



A portion of Volvox Globator still further magnified. 



He further observed that in young specimens 

 the component animalcules were perpetually 

 undergoing spontaneous fissure, the result of 

 which was the regular production of two, four, 

 eight, sixteen, thirty-two, &c. distinct animal- 

 cules from one individual, until the resulting 

 globe, i. e. the Volvox, was completely arrived 

 at its natural dimensions. 



The Volvox Globator may therefore be re- 

 garded as a hollow tegumentary vesicle, the 

 origin of which is due to the incomplete spon- 

 taneous fissure of innumerable Monads, each 

 of which is not more than 1 .500*" in diameter, 

 but all completely organised. 



Fig. 4. 



An individual monadine of Volvox Globator magnified 

 1000 diameters. 



