78 
Dr. Wallich, on the Polycystina. 
example^ Pyrosoma) are quite distinct, having each a sepa- 
rate and complete set of organs, notwithstanding that all are 
sustained within, and help to support, a common matrix. 
In the catenate Salpc^ also each member of the chain is a 
perfect Salpa, the aggregation being that merely of a colony, 
within whose limits reproduction is going on. In Tfialassi- 
colla we have precisely an analogous kind of colony ; in- 
asmuch as, in this family, but in this only among the Rhi- 
zopods, is each of the members, resident in the gelatinous 
investiture, complete in all its parts, and, as in the case of 
the Pyrosoma just referred to, a mere member of a com- 
munity.^ 
Those persons who have studied Dr. Carpenter's masterly 
classification of the Foraminifera are aware that those organ- 
isms are divided primarily into two sub-orders, namely, the 
" Perforata and the " Imperforata/^ whilst the first of these 
sub-orders is again divided into three sections, comprising such 
shells as are respectively membranous,'^ porcellanous,'' or 
" arenaceous'' in their structure ; whilst the second series 
includes only the calcareous-shelled forms. And, so far as 
physiological advance admits of demonstration from the 
characters of the shell, this basis of classification is eminently 
natural and scientific. But, with all due deference, I venture 
to express my opinion that increasing complexity in the shell 
can no more be regarded as proof of co-ordinate increase 
of differentiation in the animal portion than the fact, 
mentioned by Carpenter, that the ^'Foraminifera secrete 
sheUs unsurpassed in symmetry and complexity by those 
of any other testaceous animals/' can be accepted as 
a reason for regarding the MoUusca as inferior ta the Rhizo- 
poda. I do not deny that differences in degree of differen- 
tiation do exist. All analogy tells us they do. I merely 
maintain that where they occur they are of too subtle a na- 
ture to serve the purpose of classification, and that it has yet 
to be shown that they advance pari passu with increased com- 
plexity of the shelly covering. On this subject I cannot re- 
frain from quoting the opinion of that most able and scien- 
tific observer. Professor Williamson : 
* In Bacti/lopora (Lamarck) there certainly appears, at first sight, good 
reason to doubt this view, and the example might be regarded as excep- 
tional, were it not that this is one of the Foraminifera in which, according 
to Carpenter (* Study of the Foraminifera/ pf>. 128-9), the layer of continuous 
sarcode externally is most manifest. Williamson was the first to direct 
attention to the occurrence and use of this layer. Even in the Eozoon Ca- 
nademe there is nothing, as yet, to prove that the cavities of the mineral 
structure were not simply occupied by lobes of one and the same individual. 
