"WTLLIAD^. 



171 



Family WILLIAD^ Forbes. 



WittiadcF Forbes. British Xaked-eved Medusse. p. 19. 1S4S. 



Berenicidae Agass. {p.p. non Esch.). Cent. Xat. Hist. U. S., IT. p. 345. 1S62. 



TVILLIA Forbes. 



WUlsia Forbes. British Xaked-eyed Medusw, p. 19. 1S4S. 

 WilUa Agass. Cont. Xat. Hist. U. S.. IV. p. 346. 1S6-2. 



Willia ornata McCr. 



WUUa ornata McCr. Grmnoph. Charleston Harbor, p. 47. PI. 9. Figs. 9-11. 



TTi/Zia ornata Agass. Cont. Xat. Hist. U. S.. IT. p. 346. 1S62. 



TT7//U7 ornata A. Agass. : in Proc. Bost. Soo. Xat. Hist.. IX. Figs. -20. 21. 1S62. 



The developmeut of "Willia presents some striking differences ii"oni 

 the mode in which tentacles are regularly developed in successive cy- 

 cles, among Poh"ps. and from what has been observed, m accoixiance 

 with that mode of development, among some of oiu- naked-eyed Me- 

 dusie {Laomedea diaphana, Clytia bicophora, etc.). Li very young 

 WiUife. having only foiu' simple ch^TQiferons tubes and fotir tenta- 

 cles. — two much longer than the othei-s. as we find them in Atractylis 

 and Lafa?a. — there are soon developed four additional tentacles : these 



do not appear iu the middle between the adjoinmg chvmitei"0us tubes, 

 but about one third of the distance. (Fig. 274M ^hen this second 

 cycle of tentacles can be readily distinguished as four well-marked 

 knobs along the circular tube, an offset branches off" from the sim- 

 ple ch^-mifei-ous tube, which soon extends to the circular tube, oppo- 

 site the rudimentary tentacle ; this offset takes its origin at two thii-ds 

 the lengtli of the chymiferous tube from the circular tube ; at the same 

 time this branch is forming, the main tube is slightly bent in the op- 

 posite direction from that iu which the branch diverges : the offset 



Fig. 274*. Youngest TVillia observed, having only the second set of tentacles developed. 2, 

 second set of mai-ginal tentacles ; 2,-. branch of chiiiuifcroivs tubes leading to them. 



Fig. 275. A young AVillia. nearlv in the staae of Fig. 276. seen trom the abactinal pole. S, 

 third set of tentacles ; 3^. chvmiferous tube leadinsr to them. 



