ZANCLEA IMPLEXA. 59 



tentacles 2, set along one side with pedunculated sacs, filled 

 with thread-cells, and springing from non-ocellated bulbs at 

 the extremities of opposite canals the two intermediate 

 canals terminating in bulbous dilatations, without tentacles ; 

 a caecal tube filled with thread-cells extending, in the walls 

 of the umbrella, from the bases of the 4 tentacular bulbs, 

 and parallel to the corresponding radiating canal*. 



ACCORDING to Gegenbaur's observations, the free zooid 

 of Zanclea has four tentacles when adult. The manubrium 

 does not change with age, as in that of Syncoryne, but 

 continues short up to the time of the development of the 



ovaf- 



The characters on which the Gemmaria of M'Crady is 

 founded seem to be quite insufficient to justify its separa- 

 tion from Zanclea, if unaccompanied by important differ- 

 ences iu the trophosome. A. Agassiz believes that the 

 polypites of the two forms are most closely allied ; if so, 

 I can see no ground for retaining M'Crady's genus. 



Z. IMPLEXA, Alder. 



TUBULABIA IMPLEXA, Alder, Trans. Tynes. Club, iii. 108, t. ix. figs. 3-0. 

 COUYNE PELAGICA, Alder, ibid. iii. 103, t. ix. figs. 1, 2 (the young). 



,, IMPLEXA, Aider, ibid. v. 227- 



BRIAREUS, All-man, Ann. N. II. (July 1859), 3rd ser. iv. 54. 

 ZANCLEA IMPLEXA, Allman, Ann. N. H. for May 1864. 



Plate IX. fig. 3. 

 STEM slender, slightly and subunilaterally branched, from 



* Of these groups of thread-cells M'Crady says (Gymnophthalmata of 

 Charleston Harbour) that their " refractive power gives them a brilliancy 

 such as to remind us irresistibly of clusters of precious stones. These bril- 

 liants are set in a membranous case." 



t Vide Gegenbaur's figure, tab. viii. f. 4 i. 



