LUCERNARIDA AND GRAPTOLITIDA. 83 
CHAPTER VIIL. 
SUB-CLASSES LUCERNARIDA AND GRAPTOLITIDA. 
THE last remaining group of the living Hydrozoa is that of the 
Lucernarida, under which name are included a considerable 
number of forms, differing from one another to a great extent 
in external appearance. It will be suf- 
ficient here to describe one or two 
typical forms. 
One group of the Lucernarida is 
represented by Lucernaria itself (fig. 
27), which occurs not uncommonly in 
our own 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- 
lobed mouth. The essential elements 
of reproduction are developed within 
the body of Lucernaria itself, and it 
Fig. 27.—Two specimens of 
Lucernaria auricula at- 
tached to a piece of sea- 
weed (after Johnston). 
does not give off any generative buds, as so commonly occurs 
in other forms. 
