REVIEWS. 
375 
children for ever different from themselves. We see a single germ produce 
not one individual, but multitudes of individuals, and sometimes several 
generations, which have no relation between them of form, structure, or 
mode of life. And, lastly, we see the germ lose its primitive individuality, 
and give place to a crowd of new individualities before the products of this 
very germ are arrived at the perfect condition. 
The discoveries long since made by Peysonnel, Trembley, and others upon 
the generation of Hydra by means of gemmation and fission, and whicli 
caused at the time such universal interest, gave a great impulse to the 
early development of this question, and established the important fact that 
certain animals could, like plants, reproduce themselves by buds, appearing 
at first sight a deathblow to the doctrine of pre-existent germs. The succeed- 
ing great discovery, the origin of which is due to Chamisso, who announced 
in 1819 the alternations of generations of biphora (or salpee), seemed as 
incredible as the adventures of Peter Schlemihl, his own “ shadowless 
man.” The new doctrine was first denied ; then, when facts appeared too 
stubborn, attempts were made to explain them away ; but the succeeding 
investigations of Sars and Von Siebold established incontestably the truth 
of these extraordinary disclosures of the secret workings of nature. 
But the isolated observations of the first explorers of this new field were 
insufficient to give them any clue to the significance of these wonderful 
revelations. Modern science, however, has thrown much light upon the 
problem, and all these modes of generation are found to have something in 
common. In the case of the hydra, which reproduces itself by eggs, as 
well as by buds, it is as though there issued from the egg of a butterfly an 
animal having all the external character of the perfect insect, but deprived 
of organs ‘of reproduction, which should produce by gemmation or bud- 
ding beings like itself, and susceptible, as well as itself, of acquiring later 
the attributes of father and mother. In the case of the compound 
ascidians, it is as though the egg of the butterfly had produced first a 
caterpillar, and that this has arrived at its perfect condition ; then, on 
this butterfly issuing from the primitive egg other butterflies like the first 
have made their way (pousse ), of which the original one is, properly 
speaking, neither the father nor the mother, but only the parent. 
Geneagenesis does not exhibit itself among true mollusca ; but in the 
division of the molluscoids it appears to be the general rule. All these 
animals are more or less near in position to the biphorac. 
Among the echinodermata there appears to be a sort of connecting link 
between the two orders of facts above alluded to, and the gulf between 
the two is thus bridged. The whole animal comes under the category of 
geneagenesis ; but many of the important internal organs undergo a 
simple metamorphosis. The doctrine of spontaneous generation, which 
has so often been bolstered up by the phenomena presented by the propa- 
gation of intestinal worms, can no longer resort to this support, since it is 
now found that the remarkable phenomena of alternate generation are 
exhibited in a strongly marked manner in this division of animals. All 
the pretended agamic species are now known to be only different phases 
of development of sexual species. These changes have, in many cases, 
been accurately followed, and analogy would justify us in believing that 
