BOLINA ALATA. 



17 



the long ambulacra do not remain regularly arched, but bend towards 

 the vertical axis (Figs. 12, 

 13) ; this bend is soon 

 changed into a loop, which 

 passes through a corre- 

 sponding protuberance of 

 the spherosome. This be- 

 comes the auricle, from 

 the angle of which (Fig. 

 14) Ave also perceive a 

 branch of the chymiferous 

 tube, which soon pushes 

 its way through the gela- 

 tinous mass, and forms a 



junction with the lateral tubes, exactly as we shall find it to be the 

 case with Idyia. In the mean time the other ambulacra have been 



increasing in length, and we 

 find that they reach almost to 

 the lower end of the lobe ; 

 when there, they make a sharp 

 angle, turn upward, and form 

 thus the beginning (Figs. 12, 

 13) of the complicated system 

 of windings which we find in 

 the lobes of the adult Bohna. 

 During the later stages of 

 growth the tentacular apjsara- 

 tus has been shifting its posi- 

 tion, the opening coming nearer 

 and nearer to the level of the mouth ; the tentacular bulb lengthening 

 in proportion, and finally appearing like a long, narrow rod, with a 

 slight swelling at the extremity, from 

 which the remnants of the threads 

 of the tentacles are suspended. The 

 only changes necessary to make this 

 young an adult Bolina, are changes 

 of quantity. The apparent differ- 

 ence in the mode of growth of the 



Fig. 8. The tentacular ambulacra have united, and tBe lobes (n) project well beyond the 

 opening of the mouth. 



Fig. 9. About in the condition of Fig. 2, seen from the broad side. 

 Fig. 10. Somewhat younger than Fig. 8, seen from the broad side. 

 Fig. 11. Fig. 8, seen from the broad side. 



Fig. 12. Bolina with first appearance of the auricles, seen from the broad side. 

 Fig. 13. Bolina of stage of Fig. 12, seen from the narrow side. 

 NO. II. 3 



