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central segments. It seems probable that in all cases it can 
be entirely withdrawn within the hollow cavities of the shell- 
skeletons^ whilst it can be freely extended in every direction 
at the will of the animal. Each type of shell appears to have 
its own characteristic arrangement of the pseudopodia. In 
some^ such as the Miliol^ (fig. !)_, the long plastic filaments 
radiate only from the one terminal orifice of the outermost 
and newest segment_, there being, as we have seen, no apertures 
in their shell-walls through which pseudopodia could escape. 
But in the foraminated Eotalin^ and their alhes (fig. 2) the 
filaments stream from all the numerous apertures with which 
the shell-wall is perforated, the thin film of the sarcode 
covering at the same time all the exterior of the shell. These 
prolongations of the sarcode are doubtless the instruments 
of locomotion, but they also appear to perform other organic 
functions. As they not unfrequently embrace and invest other 
objects, such as small Diatoms, we may conclude that they 
extract nutriment from, the latter, as is the case with the 
Amoebge and Sponges. The investing layer of sarcode to 
which I have referred also appears to be the instrument in 
effecting the enlargement of the shell-skeleton. So long ago 
as 1848,* as again in 1850,f I demonstrated that, unlike the 
Mollusca, the shells of the Foraminifera must increase by 
additions to their external surfaces, and that this plan neces- 
sarily involved the continuous extension of some part of the 
soft sarcode over those surfaces. Schultze^s figure of a 
Gromia (fig. 3) thoroughly illustrates and confirms this early 
induction. It is most probable that as the pseudopodian 
threads protrude through the foramina, their bases become 
confluent outside the shell, and form the investing layer 
referred to. This explanation, if correct, brings the growth 
of these calcareous shells into close afl&nity with that of the 
skeletons of Sponges and Corals. 
It thus appears that there are no special organs in the 
sarcode of any of the Foraminifera fulfilling nutritive or other 
functions, a fact which places them in close relationship 
with the lower types of Bhizopodous animals. We may next 
inquire what is known respecting their reproduction. On this 
point our information is very scanty, the meagre result of a 
few isolated observations. The late Dr. Mantell first called 
attention, in 1846, to some small globular bodies seen in 
connection with the soft parts of Foraminifera, and which he 
suggested might be ova. Curiously enough, this observation 
* Trans. Micros. Soc. London, vol. ii., “ On the Structure of the Shell 
and Soft Animal of Polystomella crispa.” 
t Idem, vol. iii. 
