This change may be regarded either as the outgrowth of a con- 

 ical lobe from the margin oi the peristome jearing the 

 tentacle at its tip or as a conical widening of the basal por- 

 tion of the tentacle. The former vie"/ is probably the better. 

 At about this time there appear in the tentacle just beyond the 

 apex of the cone from 'vhich it springs a fe'v glistening white 

 bodies. These are the so-called otoliths and mark the begin- 

 ning of the formation of the rhopalium. Fig. 13. The tenta- 

 cles containing them will be called the rhopalial tentacles. 



These concretions, the so-called otoliths, increase in 

 number until they form a conspicuous mass, while the basal 

 cone begins to broaden laterally. This is now distinctly non- 

 contractile and may be spoken of as a mai'ginal lobe of the pe- 

 ristome. Figs. 14 and 14a show the par't of the tentacle in 

 which the concretions lie, to be covei-ed with a thicker epith- 

 elium and to be a little wider than the distal part, but this 

 may be due merely to the extended condition of the latter. 



In the specimen shown in Fig. 15, we see the first indica- 

 tion of strobilization . The upper, expanded part of the calyx 

 is separated from a conical, lower portion by a slight groove. 

 The marginal lobes have become semi -circular in outline and a 

 slight elevation is noticeable on the aboral side of each rho- 

 palial tentacle immediately external to the mass of concretions. 



- 41 - 



