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classification, we have to admit two origins, viz.: Operculata 
and Pulmonata, and then within each of these we have to admit 
convergence of characters upon which the above classification is 
based. Thus, if we consider the genera of Prosobranchiata, 
which have pulmonary sacs as forming a monophylogenetic 
group, we have to admit that they have acquired the one or two 
auricles independently. The reduction of the shell has taken 
place independently within the Pulmonata and the Opisthobran- 
chiata, and in each case is accompanied by, and may be the 
direct result of, the reflected epipodia, which gives protection 
to the visceral mass. 
In another class of Mollusca, the Cephalopoda, we find a 
very complex eye which, in certain important points, parallels 
the eye of mammals. 
As example of homoplasmy among Crustacea, I cite the 
Monstrillidae, belonging to the order Copepoda and the Rhizo- 
cephala, belonging to the order Cirripedia. Here we have some 
of the most extraordinary cases of metamorphoses, due to para- 
sitism, in the animal kingdom, and certain of the most remark- 
able features being paralleled in these two orders. Parasitism 
has taken place in many of the large groups of animals and has 
led to reduction of organs and simplification of organism, and 
numerous cases of homoplasmy can be found among them. 
Hermaphroditism is found in the Cirripedia, Isopoda, and Epi- 
carida, and have been derived independently from dioecious an- 
cestors. This condition has arisen sporadically in many groups 
of animals. 
Among insects many instances could be cited. The Honor- 
able N. C. Rothschild, in his presidential address to the Ento- 
mological Society of London in 1917, pointed out the marvelous 
cases of homoplasmy among insect ectoparasites. In these we 
find the development of ctenidia, the form flattened horizon- 
tally, the legs situated far apart and spreading, the claws often 
of peculiar form, their femora with pseudojoints, all in insects 
so far apart as Diptera, Coleoptera, Heteroptera, and Hemi- 
meridae (Orthoptera sens lat.). His concluding remarks are 
interesting : 
‘“From the various examples of resemblance I have mentioned, it is 
evident that the medium in which a species exists, exercises a most power- 
