POLYGASTRICA. 



59 



rated, the granules which circulate in the body of the hydra 

 became dyed with the juices of the animals with which it was fed, 

 precisely in a similar manner. 



The reproduction of the polygastric animalcules is effected in 

 various ways, and not unfrequently the same individual would 

 appear to propagate in two or three different modes. 



(83.) The first is by external gemmules or buds, resembling 

 those by which the hydra is multiplied which sprout like minute 

 gelatinous tubercles from the surface of the body, and, gradually 

 attaining the shape of their parent, develope the cilia characteristic 

 of their species, and soon become independent beings, although 

 they do not attain to their full growth until some time after their 

 separation. 



(84.) A second mode of reproduction is witnessed in the 

 Volvox, and others of similar conformation. In these animalcules 

 (Jig- 19, 1,) the parent is a delicate green transparent globe, which 



Ffe.19. 



under a good microscope is seen to 

 be entirely covered with cilia, whose 

 action produces currents in the water, 

 the course of which is represented by 

 the arrows in the figure ; impelled by 

 these cilia, the little globe makes its / j 

 way with a revolving motion through 

 the element which it inhabits. In 

 the interior of the volvox, the observer 

 readily discovers "other smaller globes 

 of a dark green colour, which a little 

 attention will prove to be young vol- 

 voces, exactly resembling the larger 

 one which contains them, and covered 

 in like manner with vibratile cilia, by 

 the assistance of which they swim 

 about in the body of their parent, and seem to have ample 

 space for their motions. At length, when the imprisoned gem- 

 mules are ripe for exclusion, the skin of the original volvox bursts, 

 (Jig. 19, ,) and the young ones, (Jig. 19, 8,) escaping through 

 the fissure, enter upon a wider stage of existence : yet, even before 

 their escape, the gemmules of a third generation are seen within 

 their bodies, which, gradually enlarging, are destined to terminate 

 by their birth the life of the newly liberated beings. 



(85.) The most usual mode of propagation however is by 



