240 PROCEEDINGS OF SOCIETIES. 
evidently not such as would be adopted if the protection of sar- 
code were the object in view, the subdivision into many projecting 
branches most delicate and fragile at their points exposing it as 
much as possible to every injury, and therefore presenting a form 
and arrangement not at all likely to promote the comfort and 
convenience of the animal if it were to exist long in that state ; and 
when to this we add that the pseudopodia, which are the means 
by which the Foraminifera communicate with the external world, 
are sheathed by their shell-covering so as to be incapable of 
action, and moreover that every part of the animal becomes com- 
pletely enclosed, the conclusion seems inevitable that this is not 
a condition in which it passes any considerable portion of its life, 
but that it is, as already suggested, merely the closing and final 
act. The holes through the thick shell, however, present a dif- 
ferent history ; they show by the quantity of shell-material removed 
and by the way in which separate holes have run together, that 
time has been spent in their formation, and they have also a clear 
and intelligible use in the economy of the animal, this being to 
open free communications between the internal and external sar- 
code. As to the process by which the shell-matter is removed, it 
seems impossible under the circumstances to suppose it done in 
any other way than by absorption by the sarcode in contact with 
it. Among the specimens shown is one of P. twbulosa which has 
been completely broken open, and shows that the process of 
absorption is not confined to the outer walls, but that the inner 
partitions, which at first formed parts of the walls of the separate 
chambers, are also in great part removed, throwing the whole of 
the interior into one large irregular cavity. 
The quantity of carbonate of lime deposited at once in the 
covering of the external sarcode and its pseudopodia is so con- 
siderable that some unusual source might naturally be looked for 
to supply it, and this is apparently found in the shell-material re- 
dissolved by the process just described, which must eventually 
lead to the sarcode being excessively charged with mineral matter 
and may be considered a sufficient reason for the final catas- 
trophe ; and if the view here given of the later stages of the life 
of Polymorphina tubulosa be correct, it adds another point of inte- 
rest by showing that the deposit of shell-material, in this one case 
at least, is more of a chemical than a vital act. 
