ACTINOZOA. 179 



The young Bolina, according to Mc Crady, is 

 not very unlike an adult Pleurobrachia in shape, 

 but the oral extremity appears somewhat truncate, 

 and smaller than the more rounded apical region. 

 From around the latter radiate eight short cteno- 

 phores, each containing from five to seven combs. 

 The mouth leads into a very large digestive sac, 

 tapering rapidly as it proceeds inwards to meet 

 the narrow funnel, from which are given off two 

 broad lateral sinuses, opening by eight " short 

 pointed projections" into the embryonic indica- 

 tions of the ctenophoral canals. The extremity 

 of each horizontal sinus also connects itself with 

 a wide excavation, or pit, at the side of the body, 

 from which freely issues a short tentacle, furnished 

 "vvith three or four fringing threads. Apical canals, 

 also, may be observed to the right and left of the 

 large rudiment of the ctenocyst. At a later stage 

 are developed the paragastric canals, while as yet 

 the ctenophoral tubes remain short and incomplete. 

 These last are seen to approach the apical region, 

 before lengthening so as to come near the oral 

 pole of the body. Their development would seem to 

 be somewhat in advance of that of the ctenophores 

 themselves. From the wide horizontal sinuses 

 branching radial canals soon shape themselves 

 out. The mouth gradually becomes depressed, 

 while the large antero-posterior lobes of the adult 

 animal are making their appearance. Meanwhile, 

 the tentacular pits shift, as it were, rather closer 

 to the oral extremity, until at length they arrange 

 themselves in their final position on either side 

 of the mouth. The tentacles alter very much 

 in appearance as their development proceeds, 

 becoming more numerous, but simple and less 



N 2 



