NOTES. 
327 
others arc closed, though equally filled with nourishment. The digestion of 
animal matter is very rapid ; the pachydermatous larva of an insect being ren - 
dered irrecognisable in four minutes. Vegetable matter is an inappropriate 
food, and seemingly indigestible. See Ann. des Sciences Nat. Part. Zool. tome 
viii. p. 363, &c — It were well that this anatomy of Corda was confirmed, for 
the fallacy of the microscope is almost proverbial, and powers of very high in- 
tensity must have been used in this demonstration. 
4. The nature of the Cells of the Escharidce. Page 238. 
“ If the stony cells of the Escharidse were formed by the exudation of a cal- 
careous matter which moulded itself on the surface of the secreting membrane, it 
is evident that the first layer thus formed must be the external one, and that the 
addition of new quantities of this earthy matter could only augment the thickness 
of the parietes of the cell, and modify the disposition of its interior cavity, with- 
out at all changing the exterior configuration of the first formed layer ; for here 
the solid cell completely envelopes the animal, and is not overlapped by the se- 
creting organ, as in the Mollusca gasteropoda, whose shell changes its form with 
age, because the deposit of new matter, taking place on the border of the part 
already consolidated, continually lengthens it, and is moulded on the soft parts 
whose configuration is liable to change. 
“ To throw some light on the mode of formation and on the nature of the 
cells of the Eschares, it became consequently interesting to examine these cells 
at different ages, and to see if their exterior form changed or remained always 
the same. This study, indispensable for the anatomical and physiological history 
of these little beings, may also lead to a knowledge useful to zoology and to 
geology ; for the determination of the species, recent and fossil, rests principally 
on the characters furnished by these cells ; and we are still ignorant whether or 
not they can be modified in the progress of age. 
“ This examination can be made more easily than one might at first ima- 
gine ; for neither the observation of the same individual, at different stages 
of its developement, nor the collection of a series of specimens so as to repre- 
sent all the phases through which these little creatures pass successively, is re- 
quired. Indeed, since these polypes spring from each other, and do not separate 
from their parents, each polypidom must present a long series of generations en- 
chained to each other, and in each of these series, the relative age of living in- 
dividuals must be indicated by the place which they occupy. To resolve the 
question which we have put, it is sufficient therefore to study comparatively the 
cells situated near the base of the polypidom, in its middle, in its young branches, 
and towards the extremity of the latter ; for we are certain that it is not only 
in this last place that living polypes are found, as some authors affirm, but that 
they exist over almost the entire extent of the polypidom. 
“ After examining in this manner, with a sufficient magnifyingpower, the cells 
of the Eschara cervicornis, I am quite convinced that the mode of develope- 
ment of these stony cells is not that which is usually admitted. 
“ Indeed, I have seen that not only does the general conformation of the cells 
change with age, but also that these changes operate in a great measure on the 
exterior surface, — that is to say, on that side of their parietes, which, in the 
hypothesis of their formation by layers, must exist from the first, and once con- 
solidated, ought to change no more, unless from exterior and accidental frictions. 
