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 mom delicate character than any one could have previously anticipated.
On attentively examining with glasses of high povver (1000 diameters) the minute green specks which stud the transparent covering of 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.
On closer inspection it is seen that all the Monads, which are placed at regular distances, communicate with each other by delicate threads, which form a kind of reticulation in the com inon gelatinous skin-like integument of the compound body, or polypary, as it might be aptly called, out of which the contained ani malcules only protrude their proboscides either in search of food or to row the general mass along.
It is easy to prove by flattening the Volvox between two plates of glass that its interior is only filled with water, in which sometimes there may be observed smaller volvoces swim ming about, the products of the propagation of some of the constituent animalcules. These are not solitary young ones, but may already be seen to be composed of numerous individuals, formed by the continual division of the original frotn which they sprang.
Another mode of reproduction is by the laceration or division of the globe itself. When this takes place, either for the escape of the included Volvoces generated within, or from any other cause, the component Monads im mediately prepare to leave their domiciles, and the individual animalcules become separated by the dissolution- of the inter-communicating threads ; they then, by little and little, extri cate themselves from the common gelatinous envelope, and creep out to commence an inde pendent existence. The gelatinous polypary of the original Volvox in consequence speedily loses all its green spots; and as every little point is active, moving its proboscis freely when it leaves the common globe, it may fairly be concluded that they have a power of indepen dent existence, and that each is able to begin the construction of another compound Volvox as wonderful as that we have been considering.
The development of the embryo of the Volvox is represented in 11, 12, 13, fig. 1. In 11,fig. 1, is represented the simplest con dition of a granular mass containing a clear untral spot, which in the course of a few hours assumes the condition represented in 12, fig. 1, by undergoing; an imperfect spontaneous division. By a continued repetition of this division it becomes at last broken up, until it has the appearance shewn in 13, fig. 1. The component vesicles still go on subdividing, until it assumes the appearance of a single perfect Monadine possessed of two proboscides, eye-spots, &c. By a further developement it constructs for itself an external envelope, which has the appearance of a white ring surrounding the central nucleus.