CHAPTER VIII. 



SUB-CLASSES LUCERNARIDA AND GRAPTOLITID^E. 



THE last remaining group of the living Hydrozoa is that 

 of the I/ucernarida (Lat. lucerna, a lamp), under which name 

 are included a considerable number of forms, differing from 

 one another to a great extent in exter- 

 nal appearance. It will be sufficient 

 here to describe one or two typical 

 forms. 



One group of the Lucernarida is 

 represented by Lucernaria itself (Fig. 

 22), which occurs not uncommonly in 

 temperate seas. In Lucernaria we have 

 a cup-shaped body, of a more or less 

 gelatinous consistence, usually found 

 attached by its smaller extremity to 

 sea-weeds, this end of the body being 

 developed into a small sucker. Like 

 the Hydra, however, Lucernaria is not 

 fixed, but can detach itself at will, and 

 can even swim freely by means of the 

 alternate contraction and expansion of 

 the cup-shaped body (or " umbrella," 

 as it is termed). Round the margin of 

 the cup are tufts of short tentacular 

 processes, and in its centre is fixed a 

 single polypite, furnished with a four- 



FiG.22.-Two specimens of LU- lobed mouth. The essential elements 

 cemaria auricula attached of reproduction are developed within 

 ?ohn P S ton). fSea " Weed(after the body of Lucernaria itself, and it 

 does not give off any generative buds, 

 as so commonly occurs in other forms. 



