PRELIMINARY NOTES ON COELOPLANA. 



107 



vertical canal running up to embrace the sensory organ as described by 

 Korotnef but what observations have been possible seem to point to 

 its existence in this form also. 



The mouth is large, quadrangular, with colorless lips, lying 

 directly below the sense organ. It opens into a rather thin-walled 

 pharynx, which apparently is roughly four lobed. The canals branch out 

 from above it. 



The circulation in the canals is very evident and may be observed 

 readily with a low power. The colorless fluid carries a quantity of 

 irregularly shaped bodies which frequently flow both ways in the same 

 channel. The circulation is apparently conti-olled solely by the motions 

 of the animal. 



On the dorsal surface are a series of club shaped processes which 

 may be called dorsal tentacles. They are either entire or digitate and 

 fringed ; hollow and thin walled, and communicate with the digestive 

 canals. The circulating fluid enters into them and the particles carried 

 by it whirl about in eddies within the tentacle. The tentacle itself is 

 contractile and may be withdrawn. When the animal is extended they 

 usually become obliterated. They do not seem to be particularly 

 sensitive, however, and may be moved about with a needle without 

 being withdrawn. At the base there is usually an aggregation of 

 pigment cells, tho the tentacle itself is colorless. As a result of this the 

 position of the tentacles may be noted on an extended specimen by the 

 color, when there is no sign of the tentacle itself. The arrangement 

 is hard to make out, owing to the amoeboid habits of the animal 

 mentioned above, but in the smaller brown form, they follow 

 roughly the outlines of a figure 8, covering the dorsal surface, 

 with the intersecting lines crossing at the sense organ. When floating 

 on the surface the tentacles are usually pendant and swinging in the 

 water. 



The otolith is very small, — almost insignificant in the larger form. 

 It lies in a depression closed by fleshy lips, but there are no accessory 

 sensory tentacles as described for Cfcnoplana, and no external guide 



