54 T. KOMAI : STUDIES ON TWO ABERRANT CTENOPHORES 



oral or aboral view as depicted in PI. i, figs. 6 &. "j. In the sense-organ 

 appear a few otoliths in the central part besides those existing in the 

 marginal parts mentioned before. The area representing the polar plate 

 (/• P) 'S elevated into a tranverse ridge on each side of the sense-organ. 

 A few new comb-plates are added to each rib; the cilia of each plate 

 liave grown somewhat longer. Yellowish pigment spots make their 

 appearance in the part surrounding the pharynx and in the parts about 

 the tentacular apparatuses; moreover, pigment spots looking whitish 

 by reflected light and dusky by transmitted are formed in the latter 

 parts. 



As the development advances further, the lateral compression of 

 the body grows still more remarkable, in fact to such an extent that 

 the sagittal axis measures about ^^ as long as the transverse axis. At 

 the same time, the parts neighbouring the mouth come to be demarcated 

 rather sharply off from the rest and the parts surrounding the aperture 

 of the tentacle-sheath are brought somewhat above the level of the 

 aboral sense-organ. 



In consequence of these changes, the body comes to be roughly 

 heart-shaped with a subtruncate oral end when viewed on the transverse 

 plane, and nearly pyriform when looked at on the sagittal plane. The 

 longitudinal depressions along the ribs grow deeper. The number of 

 comb-plates increases and at the same time the cilia grow much longer. 

 The movement of the larva in the egg-membrane, however, becomes 

 less active than before, on account of the want of space therein prevent- 

 ing the free movement of the long cilia. In the larva of this stage 

 (figs. 8-io), one can see in the sense-organ some ten otolithic granules 

 making an aggregate at its centre, and over the organ a highly vaulted 

 covering formed already. The comb-plates are about ten in each rib. 

 The tentacles have been greatly elongated and are of a club-like shape, 

 though as yet somewhat shorter than the height of the body even when 

 fully extended. They are now thickly beset with colloblasts on the 

 surface. The mouth aperture has widened a great deal along the 

 tentacular axis, while the internal half of the pharynx has done so along 

 the pharyngeal axis. The oesophagus likewise presents a clear lateral 

 compression, in the same direction as that half of the pharynx, and its 

 oral end is more or less produced into the cavity of the pharynx. 

 Pigment spots are now found in quantities in the parts adjoining the 

 mouth, sensory capsule and tentacular apparatuses. The existence of 

 the pigment in the superficial parts of the body renders the examination 



