PROCEEDINGS OF SOCIETIES. 239 
for though it is natural to suppose that a creature which has the 
power of precipitating carbonate of lime on its surface would also 
have the power of removing portions of it by solution or absorp- 
tion if required, the Foraminifera are so structureless that we 
should hesitate to attribute to them this function without clear 
and positive proof. 
In order to follow the successive changes in the latter part of 
the life of this Polymorphina, as they are illustrated in the speci- 
mens before you, the large rounded shells of P. communis should 
be first noticed, in which no opening is perceptible excepting the 
mouth, showing that at this stage the numerous large holes which 
are afterwards formed have no existence. The great thickness of 
the outer walls compared with that of the internal parts of the 
shell shows that the animal must have existed for a considerable 
time in this condition, during which the surface has been strength- 
ened by repeated deposits of calcareous matter from its coating of 
external sarcode, and the smoothness and evenness of this surface 
shows that the coating was at that time spread uniformly over 
the whole of it. But broken specimens of P. ¢twbulosa show that 
a change in the disposition of the external sarcode has been after- 
wards made, for in these it is found to have collected itself into 
two or three irregular bands, always commencing by one end at 
the mouth and extending towards the base of the shell, an arrange- 
ment clearly mapped out by the remains of its ultimately formed 
shell-covering, fragments of which are seen still attached to the 
surface of the smooth rounded nucleus. 
The next event in the life of this Polymorphina is the formation 
of those numerous openings through the thick shell-walls, the 
observation of which in the specimens before you has chiefly led 
me to introduce them to your notice. These show, by their defi- 
nite position and the evidence they give of their progressive for- 
mation, that when the external sarcode has once taken the form 
of bands it remains permanently in that state, and that these 
bands hold a fixed position on the parts of the shell where they 
were first placed. Among the specimens shown are some which 
only differ from ordinary shells of P. communis in being remark- 
ably smooth on the surface and in having numerous large holes 
arranged in several rows radiating from the mouth towards the 
base of the shell, exactly as in undoubted specimens of P. tubulosa, 
but they are without the slightest trace of the external arched 
coverings and tubular branches. These might at first sight be set 
down as very much rolled and worn specimens of the ordinary P. 
tubulosa, but there is no evidence in the Dogs Bay sand of other 
kinds of Foraminifera being worn to the extent which would be 
necessary to produce such a result, and the suggestion is uncalled 
for in this particular case, since it is evident that at one part of 
the life of the animal its shell must have presented the appearance 
of these specimens, unless it could be admitted that the holes are 
formed after the production of the shell-covering on the expanded 
pseudopodia. But this last is clearly a single act, and its plan is 
VOL. VII.—NEW SER. R 
