7 
Bi'itish species of the genus Lagena. 
The above opinions are at variance with those of M. Ehrenberg, 
who considers that the calcareous case of the Foraminifer is 
merely the dried skin of the animal, containing dendritic calca- 
reous particles, which on the contraction of the skin closes and 
conceals orifices through which the food is received. His ob- 
servations which led to the above conclusions were chiefly made 
upon the curious little Sorites orhiculus, Ehr., the Nummulina 
nitida of D’Orbigny. However much this organism may support 
liis opinion, certainly the Rotalina Beccarii and similar genera 
do not. AYe have no evidence that the external parietal fora- 
mina have an extensile and contractile property ; and even if the 
large orifices of Rosalina globularis had any such power, we have 
demonstrative proof that the orifices do not penetrate the lining 
membrane, into the interior of which the food would have to find 
its way. M. Ehrenberg rests his argument upon the discovery 
of small siliceous organisms in the interior of the cells. It is 
possible that the oraVl orifice may be capable of some degree of 
extension, allowing the transmission of objects of this kind. In 
Membranipora, Eschar a and other allied groups, the analogous 
parietal foramina are obviously employed for no such purpose 
as the transmission of food, which is received through the large 
orifice at the extremity of the cell. Though the fact that these 
latter objects are furnished with true polypes may make a dif- 
ference, still is it not probable that there may be a resemblance 
in the functions of such closely corresponding foramina in objects 
so nearly allied ? At the same time I may observe, that I have 
never found siliceous organisms of any size in the smaller inter- 
nal chambers of Rosalince, Rotalinfe, &c., though the frustules of 
Cocconeis, Gh'ammatophora and Navicula are not uncommon in 
the larger cells, where the communicating apertures are propor- 
tionately large. 
One of M. Ehrenbsrg^s results is much more analogous in some 
respects to those obtained by Milne Edwards, in his investiga- 
tions into the structure of Eschara. The latter ol3server has clearly 
shown that the cells of this animal are thickened by external ad- 
ditions of calcareous matter, and that, consequently, the soft 
animal membrane does not line the internal cavity, but pervades 
the whole substance of the calcareous cell ; the calcareous atoms 
not being developed upon, but in the skin of the animal. From 
this it is evident, that very difi’erent modes of growth and deve- 
lopment are to be found in animals otherwise closely allied. 
I have found that M. Ehrenberg^s remarks on the soft animals 
of the Foraminifera apply strikingly to that of Rosalina globu- 
laris, but scarcely to any other of those that I have examined. 
In this species, the animal membrane, lining the smaller cells of 
what in a shell would be called the spire, is of a rich brown co- 
