90 
absorption by the sarcode in contact with it. Among the 
specimens shown is one of P. tubulosa which has been com- 
pletely broken open and shows that the process of absorption 
is not confined to the outer walls but that the inner parti- 
tions 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 considerable that some unusual source might naturally 
be looked for to supply it, and this is apparently found in 
the shell-material redissolved by the process just described, 
which must eventually lead to the sarcode being excessively 
charged with mineral matter and may be considered a suffi- 
cient reason for the final catastrophe ; and if the view here 
given of the later stages of the life of Polymorphina tubulosa 
be correct it adds another point of interest by showing that 
the deposit of shell-material, in this one case at least, is 
more of a chemical than a vital act. 
