NOTES ON COELOPLANA BOCKI n. sp. 58! 



six or seven combs with cilia which are still very short. The tentacle 

 rudiments appear each as a slight elevation of an elongate oval outline, 

 which may be distinguished into a central and a peripheral part, both 

 gently swollen and separated from each other by a slight groove-like 

 depression. The tentacle appears to arise by prolongation of the central 

 prominence, though the tentacular epithelium is derived by extension 

 of that of the peripheral swelling. 



The mouth (o) is nearly round. The pharynx (ph) it leads into 

 exhibits also a roundish outline in optical cross-section. The inner end 

 of pharynx lies nearly midway between the oral and aboral poles of 

 the body. A short process at the inner end of pharynx indicates the 

 oesophagus ipe). 



In slightly more advanced larvae, the body presents a distinct lateral 

 compression, it growing longer in the transverse axis than in the sagittal. 



Meanwhile, the tentacle-stem makes its appearance in the area 

 indicated above, at first as a tubercle-like prominence ; the cilia of 

 comb-plates lengthen ; the mouth widens, elongating in the transverse 

 direction, while the inner half of pharynx becomes compressed in the 

 sagittal direction. 



As the development still advances (Fig. 4), the lateral compression 

 of body grows to the extent that the length of the sagittal axis measures 

 about 2/3 that of the transverse axis. At the same time, the oral 

 region is somewhat produced, so that the body now appears roughly 

 heart-shaped with subtruncate oral end when viewed on the trans- 

 verse plane (Fig. 4), but nearly egg-shaped when seen on the sagittal 

 plane. The number of comb-plates in each row increases up to about 

 ten, their cilia growing at the same time very considerably in length. 

 A highly vaulted covering has now formed over the sensory cavity ; 

 and the otolith, forming a single mass of seven or eight granules, has 

 assumed a central position in the cavity. The tentacles if) have greatly 

 elongated and have assumed a club-like shape ; they are now thickly 

 beset with colloblasts on the surface. The mouth (o) has widened 



