230 Miscellaneous. 
one and the same species is particularly striking among the Cteno- 
phoree. In this order there are not even sexual differences among 
the individuals, as they are all hermaphrodites. In the Discophoree 
proper a somewhat greater diversity prevails. In the first place, we 
notice male and female individuals; and the difference between the 
sexes is quite striking in some genera, as, for instance, in Aurelia. 
Next there occur frequent deviations among them, in the normal 
number of their parts,—their body consisting frequently of one or two 
spheromers more than usual, sometimes even of double the normalnum- 
ber, or of a few less. And yet, year after year, the same Discophoree 
reappear upon our shores, with the same range of differences among 
their individuals. Among Hydroids polymorphism prevails to a greater 
or less extent, besides the differences arising from sex. Few species 
have only one kind of individuals. Mostly the cycle of individual 
differences embraces two distinct types of individuals, one recalling 
the peculiarities of common Hydre, the other those of Meduse ; 
but even the Hydra type of one and the same species may exhibit 
more or less diversity, there being frequently two kinds of Hydre 
united in one and the same community, and sometimes even a larger 
number of heterogeneous Hydre. And this is equally true, though 
to a less extent, of the Medusa type. Yet among Siphonophoree 
there are generally at least two kinds of Medusze in one and the 
same community. But, notwithstanding this polymorphism among 
the individuals of one and the same community genetically connected 
together, each successive generation reproduces the same kinds of 
heterogeneous individuals, and nothing but individuals linked together 
in the same way. Surely we have here a much greater diversity 
of individuals, born one from the other, than is exhibited by the 
most diversified breeds of our domesticated animals; and yet all 
these heterogeneous individuals remain true to their species, in one 
case as in the other, and do not afford the slightest evidence of a 
transmutation of species. 
Would the supporters of the fanciful theories lately propounded 
only extend their studies a little beyond the range of domesticated 
animals, would they investigate the alternate generations of the 
Acalephs, the extraordinary modes of development of the Helminth, 
the reproduction of the Salpze, &c., they would soon learn that there 
are in the world far more astonishing phenomena, strictly cireum- 
scribed between the natural limits of unvarying species, than the 
slight differences produced by the intervention of man among do- 
mesticated animals, and perhaps céase to be so confident as they 
seem to be that these differences are trustworthy indications of the 
variability of species. For my own part, I must emphatically declare 
that Ido not know a single fact tending to show that species do vary 
in any way, while it is true that the individuals of one and the same 
species are more or less polymorphous. The circumstance that 
naturalists may find it difficult to trace the natural limits of any one 
particular species, or the mistakes they may make in their attempts 
to distinguish them, has nothing whatsoever to do with the question 
of their origin. 
