252 
ZOOLOGICAL LITERATURE. 
placed between the Mollusca proper^ on the one hand^ and the 
Protozoa, on the other. The members of the group thus con- 
stituted; though developed from true ova, are prone to form 
compound organisms by continuous gemmation. In all, the 
movement of the circulatory fluid is effected either by ciliary 
action or by a propulsive organ unfurnished with valves. 
This new arrangement mainly depends on its author^s inter- 
pretation of certain structures of the Ctenophora, especially of 
Cydippe. The funnel and apical canals of this organism he 
regards ns an intestine; not as parts of the general cavity of the 
body. He also considers it probable that the ciliated bands of 
Cydippe represent the tentacula of the Polyzobn or of the 
Brachiopod having become retroverted and connate; as it were, 
with the body; as next in order of suppression.^^ These structures 
are without corresponding organs among the Coelenterata proper; 
which want; moreover; the nervous system common to the 
Mulluscoida and Ctenophora. The acpiiferous system of Cydippe, 
like the pallial sinus system of the Brachiopod, is not only 
lined with cilia circulating a corpusculated fluid; but also con- 
tains the reproductive organs.'’^ So, likewise, the tentacular 
apparatus of the Ctenophora may be regarded as pallial. 
Accepting the conclusion that the branchial sac of the Tuni- 
cat a is represented by the tentacles of the Polyzoa or the fringed 
arms of the Brachiopoda, our author assigns it a further homo- 
logue in the ciliated bands of the Ctenophora. Accordingly 
this class would belong rather to the Molluscoid than to tlie 
Coelenterate division of the proposed series, while “ the Brachu 
opoda and Polyzoa should be taken together as a group in them- 
selves, quite as natural as the Tunicata, consisting of simple and 
compound forms.'*^ Comparing, therefore, the respiratory sys- 
tem in these three classes of the revised group of Molluscoida, 
it will be pharyngeal in the first [Tunicata or Ascidiozoa^, oral 
in the second [Brachiopoda and Polyzoa^ , and somatic in the 
last [Ctenophora'] The entire classification is summed up in 
the accompanying table — 
Molluscoida (including the Ctenophora ) — 
[With primary h£emal [ * -t. 
Intestine insulated from the j and final neural flexure \ iczoa. 
somatic ca\ity. 1 With simple neural \ Brachiopoda 
( flexure [ and Polyzoa. 
Intestine straight, and communicating with the so- 
matic cavity 
Coelenterata (excluding the Ctenophora ) — 
Intestine obliterated ; stomach communicating with 
the somatic cavity 
True stomach obliterated, its office being answered by 
the somatic cavity 
I Ctenophora. 
I Actinozoa. 
I Hydrozoa. 
Thus, from the Ctenophora as a central group, we proceed in 
