ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 797 



only three or four. They arc generally found in greatest numbers 

 near the head, and especially near the mouth ; but this is not always 

 the case. Lastly, they do not appear to be injured by being expelled 

 from the body, for their movements are then often twice as energetic. 

 These reasons, however, do not appear to the author to be conclusive. 

 Against them there is the fact that Puhatcllse have never been found 

 swimming freely in the water in which the Convoluta dwells. 

 Another hypothesis is possible — that they are cells of the body of the 

 animal which have projected into one of the cavities of the reticulum, 

 and have become differentiated into a small organ capable of pro- 

 ducing movements of the contained liquid. Their development, how- 

 ever, remains to be worked out. Analogy helps us so far that in 

 Guncla Lang has discovered ciliated infundibulate cells mixed with 

 those of the intestine, and has admitted the possibility of the 

 analogous cells in the parenchyma being migrants from the intestinal 

 layer. The question is one which can only be solved by a history of 

 their development. 



Cephalic Pits of Nemertines.* — M. Eemy de Saint Loup thinks 

 that the cephalic pits of the Nemertinea may be strictly compared to 

 the essential forms of the segmental organ of the Hirudinea, from 

 which they only vary in structure and function. They may serve as 

 auditory organs, as an irrigating and respiratory apparatus, or as a 

 head-kidney. 



Ctenoplana Kowalevskii.j — Dr. A. Korotneff describes a remark- 

 able new form which appears to be allied to Goeloplana metschnikowii. 

 He found it at a small coral-islet, Pulu Pandau, off the west coast of 

 Sumatra. Externally it is quite flat and round, and measures about 

 6 mm. in either direction. It creeps about like a planar i an on its 

 ventral surface, in the centre of which there is the rounded mouth. 

 On the middle of the dorsal surface there is an otolith-vesicle ; the 

 line which joins this with the mouth may be regarded as the primary 

 axis. In the middle of the anterior and of the posterior margin there 

 is a notch, and the plane which unites them and passes through the 

 primary axis may, in accordance with Chun's terminology of the 

 Ctenophora, be called the gastric plane. Along this plane the animal 

 folds itself when it sinks from the surface to the bottom of the water. 

 In such a position one best sees a thickening of the surface, which 

 extends backwards and forwards into two blunt points. Right and 

 left there are three similar points, and they all give a stellate appear- 

 ance to the thickening. Between these rays there are cleft-like 

 orifices, which inclose ctenophoral plates, which are capable of pro- 

 traction and retraction. 



The transverse plane, and that at right angles to the gastric, 

 inclose two tentacles, the presence of which can only be detected in 

 sections. In colour, Ctenoplana is rosy above and yellowish below ; 

 the margin of the body is transparent. 



As in Goeloplana the tentacles are solid, the lumen being occupied 



* Comptee Rendus, cii. (1S8G) pp. 157G-8. 



f Zeitschr. f. Wis*. Zoo!., xliii. (18SG) pp. 242-51 (1 pi.). 



