g2 ZOOLOGY 
The family Mierostomida is unique in the group in possess- 
ing the property of asexual reproduction, which takes place by 
transverse fission. The posterior third of the 
body becomes cut off by a septum, and grows 
until it equals in size the anterior half. 
Then each portion again cuts off its posterior 
third, and these again grow (Fig. 64). By 
this process of segmentation and equalisa- 
tion chains of 4, then 8, then 16, and some- 
times even 32 individuals are formed. Each 
forms a mouth, and for some time the chain 
persists, but the individuals ultimately 
become sexually mature and then separate. 
They lay eggs during the autumn, which 
persist through the winter, and these give 
rise in the spring to the budding individuals. 
Two curious animals, the Coeloplana and 
the Ctenoplana, have recently been described 
by Kowalevsky and Korotneff respectively, 
which are intermediate in structure between 
the CTENOPHORA and the TURBELLARIA. 
Coeloplana is minute, its flattened body 
covered with cilia, creeps along the surface 
on its ventral face. In the middle of its 
back is a sensory vesicle enclosing an otolith. 
Fic. 64.—Microstoma On each side of its body, at right angles to 
lineare, Oe.» under the plane of the stomach, is a long feathered 
going division. There 
are 16 ecu enn 8 tentacle which can be withdrawn into a 
ith mouthapertures, ; A 
Aaa the-pade o¢ pouch. The mouth in the middle of the 
the first (m), second ventral surface opens into a stomach which 
(m’), third (m”), and. , : 1 
fourth (m’”) genera- gives off numerous anastomosing canals, two 
tion, The fifth gen- of which pass dorsally, one in front and one 
eration has not yet : ; 
acquired a mouth behind the otocyst, and there end blindly. 
ee patee Von Ctenoplana has much the same shape as 
£ be Y 7 ajo . . 
eG aiateade coves: Coeloplana. In addition to the uniform 
2. Eye spots. covering of cilia, there are on the dorsal sur- 
3. Intestine. 5 c 
face eight bands of etenophoral plates corre- 
sponding to those of the Ctenophors. The alimentary canal 
resembles that of Coeloplana. The sense organ, situated in the 
