172 REVIEWS—CONTRIBUTIONS TO NATURAL HISTORY. 
Those who only know the compound Acalephe animals, which 
comparatively few naturalists can study in the living state, from the 
descriptions given in the ordinary books may be surprised at the 
above statements, which nevertheless they will soon find to shed a 
beautiful light over the whole of a very obscure subject. 
The fifth section of this chapter on “Individuality and specific 
differences among Acalephs,” furnishes our author with an occasion 
for remarks on Darwin’s “‘ Origin of Species,” in which he earnestly 
and powerfully opposes the views of that writer, which now occupy 
so large a share of the attention of the lovers of Natural Science. 
In a former number of this Journal we copied from Silliman’s 
journal the extract on this subject from the then unpublished volume 
now before us, and we only add a short passage which strongly 
expresses the convictions of one who eminently unites Philosophy 
with varied and novel practical observation in his researches. After 
referring to the polymorphism of the lower Acalephe, he goes on 
to say :-— 
-“ But, notwithstanding this polymorphism among the individuals of one and 
the same community generically connected together, each successive generation 
reproduces the same kinds of heterogeneous individuals, and nothing but indivim 
duals, linked together in the same way. Surely, we have here a 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 Helminths, the 
reproduction of the Salpz, &e. &e., they would soon learn that there are in the 
world far more astonishing phenomena, strictly circumscribed between the natural 
limits of unvarying species, than the slight differences produced by the interven- 
tion of men, among domesticated animals; and perhaps, cease 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 I do 
not know a single fact tending to shew that species do vary in any way, while it 
is true that the individuals of one and the same species are more or less polymor- 
phous. The circumstance that naturalists may find it difficult to trace the 
natural limits of any one particular species, or the mistakes that they may make 
in their attempts to distinguish them, has [have] nothing whatsoever to do with 
the question of their origin.” 
‘We must not pretend to follow the learned author too closely 
through the contents of so large a volume. He establishes the 
claim of the class Acalephee to the Ctenophoree, which some distin- 
