76 ZOOLOGY 
on the other hand two curious organisms, the Coeloplana of 
Kowalevsky and the Ctenoplana of Korotneff, have lately been 
discovered which unite some characters of the Ctenophora 
with others of the Turbellaria. 
In a typical Ctenophor, one of the Cydippidae, such as 
Hormiphora, the mouth leads into a flattened stomach lined 
with ectoderm, which in its turn opens into the funnel, lined 
with endoderm (Fig. 53). The funnel gives off two gastric canals, 
which pass out towards the base of the long tentacles. These 
two primary canals give off a secondary canal on each side, 
which forks, and forms tertiary canals (Fig. 54), of which there- 
fore there are eight. Each of these eight canals opens into 
one of eight meridional canals which lie under the rows of 
vibratile plates, and which end blindly both at the oral and 
aboral pole. 
The two long tentacles can be completely retracted into their 
pouches ; they bear peculiar adhesive cells. 
The characteristic vibratile plates are formed by a number 
of very large cilia fused together side by side; an arrangement 
also met with in some of the Hypotricha. 
The central nervous system consists of an area of ciliated 
Fic. 54.—Hormiphora plumosa. 
After Chun. Aboral view. 
2. Aboral pole with sense organ. 
5. One of the eight bands of 
fused cilia. 
6. One of the eight canals running 
towards 5. 
8. A tentacle. 
9. Gelatinous tissue. 
SS. sagittal plane. 
cells at the aboral pole. This area is sunk into a depression 
which contains certain otoliths, and from which nerve cells 
pass to the meridional rows of paddles. This specialised sensory 
