The analogy between the plant and the animal in their functions of reproduction is nowhere more evident or more curious than in a vegetable production which abounds in the waters of the Rhône, and has received the name of _Vallisneria spiralis_. In this plant the male and female organs are placed on different branches of the same plant. The female flowers are fixed to the ground by long, twisted, spiral stalks. But, when seeding time comes, the spirals of the stems unroll themselves, and the female flowers come up to the surface of the water and spread themselves out. The male flowers, not being placed like the female on elastic stems, cannot come up to the surface of the water. What do they do? They burst through their covering, and float around their females on the surface of the water. After that the current carries away the detached male flowers; and the female stem folds itself up again, and sinks to the bottom of the river, there to ripen its impregnated ovules.
The function of reproduction in plants is rich in conclusions in support of our thesis. The plants called phanerogamous are not reproduced only by impregnation by means of the visible sexual organs, the pistil and the stamen, they are also multiplied by grafts, buds, and cuttings. Cryptogamous plants, which have no sexual organs, are multiplied either by effects which detach themselves from the individual plant at a certain period of its vegetation as we see in the case of fungi, algæ, mushrooms, &c., or by fragments of the individual itself, which, being thrown into the ground, germinate and multiply themselves.
Animals, in their several classes, represent all these modes of reproduction; there is not one which does not exist among them. Animals are not reproduced by eggs only, either interior or exterior, and by living young ones, they are equally multiplied, like vegetables, by offsets, by cuttings, and by ingraftment.
Multiplication by offsets may be observed in the fresh-water polype. Little buds which grow and lengthen come out of the body of this animal. While the bud is lengthening, he throws off other and smaller offsets, which throw off still smaller ones. All these are so many little polypes, which derive their nourishment from the principal polype. Having attained a certain size, these offsets separate themselves from the primitive individual, and constitute so many new polypes. Coral multiplies itself in the same manner. From the principal branch spring secondary branches which have originated in a bud or shoot, and these branches, inserting themselves into the chief stem, form new individuals. Thus the exterior aspect of the coral resembles a ramified tree rather than an animal.