STRUCTURE AND DEVELOPMENT OF COELOPLANA. 31 



in the sagittal plane. However, as far as my observation goes, such 

 canals are never present, there being two perradial canals only, which 

 start from the transverse sides of the infundibulum. He further maintains 

 that, the meridional canals of ordinary ctenophores are entirely obliterated 

 in Coeloplana. But there is no room for doubting that, the subpharyngeal 

 and subtentacular canals do represent the meridional canals: those 

 canals are lined with a tall palisade epithelium on the dorsal side and 

 the gonads take their origin in that epithelium, precisely as it is the 

 case with the meridional canals of the ordinary ctenophores. Ahbott 

 further denies the existence of cilia in the endodermal parts of the canal 

 system. However, the ciliation is easily observed in any part of the 

 low epithelium, provided the material be preserved toIerabU' well. The 

 same fact is given in Kkempf's work ('21). But it is rather noteworthy 

 that, the palisade epithelium of the subpharyngeal and subtentacular 

 canals shows distinct ciliation, since the epithelium of the meridional 

 canals of ordinarx' ctenophores is devoid of cilia in that part. 



Krempf ('21) distinguishes two canal systems in Coeloplana, which 

 he named " reseau meridien ou reseau gonadien " and " reseau pharyn- 

 gean " respectively. According to him, the former represents the 

 meridional canals and their branches of ordinary ctenophores, and the 

 latter the pharygeal canals and their branches. But, so far as my 

 observation has ascertained, canals which may be identified with the 

 pharyngeal canals of ordinary ctenophores seem to be wanting in 

 Coeloplana. The pharygeal canal of ordinary ctenophores is sent out 

 from the perradial canal at a point generally somewhat proximal to the 

 branching of this canal into interradial canals. Moreover, the pharyn- 

 geal canal shows a ridge-like tract along each sagittal side of its wall. 

 In Coeloplana, however, canals with such distinguishing features can not 

 be recognized altogether, and all the canalar network in the regions 

 about the pharynx are the branches of the subpharyngeal canals. 



G o )i ads. 



Since both Kowalevskv and Abbott could not observe gonads in 

 Coeloplana, the genital system of this interesting animal has remained 

 unknown. Certain [previous writers expressed their expectation a priori 

 that, such an aberrant form would present a good man)- peculiarities when 

 the condition of the gonads would be made out. And the fact is just 

 as it had been expected, there are indeed several highly characteristic 



