TOO 



MANUAL OF ZOOLOGY. 



ORDER I. LUCERNARIAD^E. This order includes those Liicer- 

 narida which have only a single polypite, are fixed by a proximal 

 hydrorhiza, and possess short tentacles on the margin of the um- 

 brella. The reproductive elements " are 

 developed in the primitive hydrosoma 

 without the intervention of free zooids." 

 (Greene.) 



In Lucernaria (fig. 22), which may be 

 taken as the type of the order, the 

 body is campanulate or cup-shaped, 

 and is attached proxirnally at its smaller 

 extremity by a hydrorhiza, which, how- 

 ever, like that of the Hydra, is not 

 permanently fixed. When detached, 

 the animal is able to swim with toler- 

 able rapidity by means of the alternate 

 contraction and expansion of the um- 

 brella. Around the margin of the um- 

 brella are tufts of short tentacular proces- 

 ses, and in its centre is a polypite with 

 a quadrangular, four-lobed mouth. " In 

 transverse section the polypite may be 

 described as somewhat quadrilateral, 

 with a sinuous outline, which expands 

 at its four angles to form as many deep 

 Fig. 22. Lucernaria. Lucer- longitudinal folds, within which the 



narta auricula attached to . , . i j 1-11,1 



a piece of seaweed. (After simple generative bands are lodged.' 

 (Greene.) Wide longitudinal canals 



are formed by septa passing from the walls of the polypite to 

 the inner surface of the cup, and a circular canal runs imme- 

 diately beneath the insertion of the tentacles. The reproduc- 

 tive elements are produced within the body of Lucernaria itself, 

 without the intervention of any generative zooid, 



ORDER II. PELAGID^E. This order is defined as including 

 Lucernarida, which possess a single polypite only, and an umbrella 

 with marginal tentacles. The reproductive elements " are devel- 

 oped in a free umbrella, which either constitutes the primitive 

 hydrosoma, or is produced by fission from an attached Lucerna- 

 roid. " (Greene. ) 



Two types, therefore, exist in the Pelagidcz. The one type 

 is represented by a fixed "trophosome," resembling Lucernaria, 

 but distinguished from it by the fact that the generative ele- 

 ments are not developed in the primitive hydrosoma, but in a 

 free "gonosome," which is produced for the purpose. The 

 second type, represented by Pelagia itself, is permanently free, 



