COELENTERATA 77 
apparatus possibly serves as a balancing organ, and helps to 
keep the floating animal the right way up. 
The reproductive organs are arranged along the meridional 
canals, the male cells on one side and the female cells on the 
other of each canal. The ova and spermatozoa escape through 
the canals, and eventually leave the body through the mouth. 
The main features of the anatomy of the Ctenophora have 
been indicated in order to render intelligible their possible 
relationship on the one hand to the Anthomedusae and on the 
other to the Turbellarians. There is a mass of interesting 
detail with reference to these animals which cannot be referred 
to here. 
The Anthomedusan Ctenaria has the mouth of its umbrella 
very much contracted, and the edges have grown round and 
over the manubrium, which is small. The opening into this 
sub-umbrella cavity corresponds with the opening into the 
stomach of the Ctenophor ; and the lumen of the latter, lined as 
it is with ectoderm, corresponds with the sub-umbrella cavity 
of Ctenaria. The shape of the medusa is very like that of 
Cydippe, and its surface is provided with eight rows of modified 
ectodermal cells, which correspond in position with the 
eight rows of vibratile plates in Ctenophors. The arrange- 
ments of the enteric canals also approaches that of Cydippe, 
and the resemblance between the two animals is further in- 
creased by the presence in both of two long fringed tentacles 
which project from pouches as in the Ctenophora. 
The Cestus veneris, or Venus’s girdle, is a Ctenophor in which 
the spherical form has been replaced by a flattened band-like 
shape. It is found swimming at the surface of warm seas, and 
moves through the water by a series of graceful undulations. 
Beroe, in which the stomach attains a very great size, has no 
tentacles. 
The group is a carnivorous one, the chief food being pelagic 
organisms. Many of them are phosphorescent. 
