the fact that Hydroids of an entirely distinct character may produce similar Jelly-fishes. [Illustration: Fig. 50. Aurelia flavidula, seen from above; _o_ mouth, _e e e e_ eyes, _m m m m_ lobes of the mouth, _o o o o_ ovaries, _t t t t_ tentacles, _w w_ ramified tubes. (_Agassiz_.)] The embryos or little planulæ, hatched from the Cyanea and Aurelia in the fall, seem to be gregarious in their mode of life, swimming about together in great numbers till they find a suitable point of attachment, and assume their fixed Hydroid existence. The Cyaneæ, however, when adult, are usually found singly, while the Aureliæ, on the contrary, seek each other, and commonly herd together. _The Campanella_. (_Campanella pachyderma_ A. AG.) [Illustration: Fig. 51. Campanella seen in profile; greatly magnified.] [Illustration: Fig. 52. Same, seen from below.] The Campanella (Fig. 51) is a pretty little Jelly-fish, not larger than a pin's head, reproduced directly from eggs, without passing through the Hydroid stage. During its early stages of growth it probably remains attached to floating animals, thus leading a kind of parasitic existence; but as its habits are not accurately known, this cannot be asserted as a constant fact respecting them. The veil in this Jelly-fish is very large, forming pendent pouches hanging from the circular canal (see Fig. 51), and leaving but just room enough for the passage of the proboscis between the folds. It may not be amiss to introduce here a general account of this organ, which occurs in many of the Medusæ, though it has very different proportions in the various kinds. It is a delicate membrane, hanging from the circular tube, so as partially to close the mouth of the bell, leaving a larger or smaller opening for the passage of the water, which is taken in and forced out again by the alternate expansions and contractions of the bell. There are but four chymiferous tubes in the Campanella, and four stiff tentacles, which in consequence of the peculiar character of the veil appear, when the animal is seen in profile, to start from the middle of the disk. The ovaries consist of eight pouches, placed near the point of junction of the four chymiferous tubes. (Fig. 52.) This little Medusa is of a dark yellowish color with brownish ocellated spots, scattered profusely over the upper part of the disk. _Circe_. (_Trachynema digitale_ A. AG.) [Illustration: Fig. 53. Trachynema digitale; about twice the natural size.]