206 Mr. Toulmin Smith on the Classification 
tra, be found to this general rule, — both external and internal 
surfaces of the Ventriculidse were polypiferous. And notwith- 
standing the closeness of the folds in many species, I believe that 
the inner parts of all the folds were polypiferous also. The in- 
quirer familiar with recent Polyzoa will find no ditficulty in 
realizing this as true, as he will be aware that these minute crea- 
tures are often packed in spaces so close, that it would seem to be, 
and perhaps is, impossible that all should be protruded at the same 
time. This fact has attracted the attention of all observers. 
Dr. Farre notices that the individuals of Halodactylus diaphanus 
“ are so closely set that there seems to be hardly room for 
their several operations and that, on this account, it is often 
scarcely possible to make any observations upon them^"’ even 
with the microscope*. And the most recent writer on the 
Polyzoa, Sir J. G. Dalyell, in his ^ Remarkable Animals of Scot- 
land,^ calls attention several times to the extreme complexity of 
the mass and to the difficulty of even microscopic observation 
on that account t- And in the plates of both these writers 
(pi. 25. fig. 1, Farre ; pis. 43, 44 A, &c. Dalyell) the same fact is 
well shown. It thus becomes obvious that, in recent allied forms, 
individuals are packed in positions quite as close as, if not closer 
than, in any of the Ventriculidse, and in positions apparently 
more hazardous to the free action of the individuals themselves, 
inasmuch as the form of the recent species specially referred to 
is less fixed and unyielding than, from the very nature of their 
structure, the Ventriculidse have been shown to have necessarily 
been. 
Having thus shown that there is no improbability that in fossil 
forms the surface should have been thus closely covered, in all 
its parts, by the polyps, I will add, that the results of positive 
observation establish the fact that the inner parts of the folds in 
the Ventriculidse were thus polypiferous. I have carefully dis- 
sected several folds in specimens, both in chalk and flint, in 
which the fold is the closest of any species, and I have found, by 
aid of the microscope, the presence of the polyp-cells clearly and 
unequivocally marked. 
With respect to the arrangement of the fold, the elaborate dis- 
section of many individuals of more than thirty difierent forms 
of Ventriculidse has fully satisfied me that here, as elsewhere, 
Unity is prevalent ; and that the fold of the membrane forming 
the wall of the pouch is not capricious and without method or 
principle, as at first sight it might appear. I have fully satisfied 
myself that every form and variety of foldj which different 
* As before, p. 40.5. 
I See, inter alia, pp. 2.33, 234, as to Celhilaria loriculata. 
t It is necessary to distinguish the folding of the membrane forming the 
