less conspicuous ; and it is the recognition of its existence despite 
the modifying power of interfering circumstances, which, to my 
mind, at least, imparts a perfect charm to study of the sub-sciences 
of Physiological Botany and Comparative Anatomy, enabling us to 
interpret accurately the signification of every structural and morpho- 
logical peculiarity, whether it occur in the human economy, or in 
the framework of any plant or animal. 
For the partial recognition of the bearings of this law— which 
Von Baer has defined as the “ law of development from the gene- 
ral to the special”— as well as for the full understanding of its cha- 
racter, it is fortunately not necessary that our studies should embrace 
the whole range of Botanical or Zoological Science, — although, of 
course, our conceptions of its power and universality are enlarged 
to a degree precisely corresponding with the range and direction of 
our pursuits ; and as this community of plan, associated with 
variety of purpose, is not confined to any particular series of organs 
or organisms, it consequently follows, that (in order to meet the 
varied requirements of the several creatures in which special deve- 
lopments occur) we find the same series of homologous structures 
strangely modified in form and function to suit the foreknown exi- 
gencies of every species. 
From the tenor of this last observation, it might seem very natu- 
ral that I should revert to the seemingly opposed theories of Cuvier 
and Geoffroy St Hilaire ; but the points in their dispute have been 
so frequently commented on by abler speakers, that I shall only offer 
a passing remark : — I think we may fall in with the spirit of the 
Cuvierian hypothesis, and say thus much, at least, viz., that the 
totality of the phenomena presented by any individual, species, 
genus, or. natural group of beings, indicates a distinct provision for 
the preservation and perpetuation of the individual, species, &c. ; 
this provision being limited by the operation of antagonistic forces 
from within and without, necessary to the welfare of other co-existing 
species, &c. ; and that the balance of these mutually-opposing 
influences is in the main progressive, conservative, and perfective. 
I have no wish now, however, to pursue this question further, 
otherwise I should be led to take into consideration Mr Darwin’s 
theory in relation to the origin and succession of species. In regard 
to the hypothesis of Geoffroy St Hilaire, in so far at least as it applies 
to the development of particular organs, it is clearly manifest 
that mahy structures exist without the slightest utilitarian purpose 
being subserved by their presence ; these are mere type-manifesta- 
tions or morphological indications of some organ whose assumed 
completeness may, or may not, be present in some other living or 
pre-existing allied species. 
As an illustration of this, allow me to direct your attention to the 
occurrence of a singular pouched structure which I have dis- 
covered in connection with the ileo-colic valve of the alimentary 
canal of the Giraffe ; 
