192 CAMPANULINLD^E. 



Agassiz, only four are present. They are developed from 

 the digestive cavity, and gradually extend downwards, 

 opening at last into the circular vessel. Sometimes two 

 or three rudimentary tubes of various lengths are met 

 with between each of the perfect canals. The fimbriated 

 mouth of the manubrium is a striking feature; indeed 

 the whole structure is complex, and there is an extra- 

 ordinary multiplication of parts. It is curious that the 

 only one of these comparatively gigantic organisms that 

 has been traced to its stock should prove to be the repro- 

 ductive phase of one of the smallest of the Hydroida. 



Though there is so much superficial difference between 

 the adult gonosomes of Campanulina and Zygodactyla, 

 there can be little doubt that these genera should be 

 ranked in the same family. The trophosomes are identical ; 

 and in their earliest condition there seems to be no essen- 

 tial difference between the gonozooids. Those of Zygo- 

 dactyla have probably only four radiating canals at the 

 time of liberation, the number increasing, like that of the 

 tentacles, as they advance to maturity. In Campanulina 

 the arms multiply, but the canals seem never to exceed four. 



Z. VITRINA, Gosse. 



^EQUOREA VITRINA, Gosse, Devonsh. Coast, 340, pl.xxiii. ; T. S. Wright, Journ. 



of Micr. Science, iii. (N. S.) 45, pi. iv. figs. 1-6. 

 ZYGODACTYLA VITRINA, Agassis, N. H. U. S. iv. 361. 



Plate XXXVIII. fig. 2. 



STEM simple (or branched?); HYDROTHEC/E squared below, 

 and above terminating in many convergent segments; 

 POLYPITES with 12 alternating tentacles, united for about 

 a third of their length by a web ; GONOTHEC.E unknown. 



GONOZOOID. UMBRELLA hemispheric or subconic, perfectly 

 colourless ; MANUBRIUM wide, traversed by opake white 

 lines, and with very numerous, narrow, pointed, furbe- 



