122 STARFISH GALLERY. 
shown which give a good idea of the structure of the female and the 
smaller male. The young make their way through the walls of the 
stomach of their host, and encyst themselves among its muscles : a 
piece of a sternothyroid muscle is shown, taken from a man in whose 
body it was calculated there were forty millions of encysted Trichince. 
Other Nematodes infesting man, such as Filaria sanguinis 
hominis, are too small for exhibition. 
Plants are not free from the attacks of Nematodes, and examples 
are shown, accompanied by an illustrating figure, of the Ear-cockle 
gall of wheat ; this gall is due to the injuries inflicted by a minute 
Thread- worm — TyJenchus tritici. Wheat is, of course, by no means 
the only cultivated plant that is attacked by these minute worms ; 
the history of most has, however, still to be made out. 
Holding a somewhat uncertain position in relation to the Round- 
worms are the parasitic Acantliocephctli (Thorn-headed Worms) and 
the free-swimming Chcetognatha, or Bristle- jawed Worms ; examples 
of both of these groups are shown, together with diagrams illustrative 
of their general structure. 
Annulata or Chsetopoda. — So-called because consisting of a 
series of rings, and being provided with chaetae or bristles ; they 
are to be associated with the Arthropoda, under the one head 
" Appendiculata," a better name than " Articulata," since Cuvier did 
not include worms in his group. The creatures that are most 
familiarly called worms are to be found in Case III. ; here are a 
few examples of the numerous kinds of w T orms that are found living 
freely in the sea, of earth and freshwater Worms, and of Leeches. 
All these worms are distinctly characterized by the fact that they 
consist of a number of definite rings (somites), whence they have 
been called Annulata. The marine Worm and the Earthworm differ 
from the Leech in that these rings are provided with chastaa or 
bristles, of which there are a number in each bundle in the marine, 
and a few only in the terrestrial or freshwater form : hence the 
marine Worms are called Polychcvta and the latter Oligochceta. 
The former are divisible into two great groups. There are those 
that are free-swimming and are able to forage for themselves, such 
as the lovely Sea-mouse (Aphrodite aculeata), the large Eunice 
gigantea, the common Nereis pelagica, or the exquisitely coloured 
Chloeia flava. Others live a more retired life, dwelling in tubes, 
which they fashion for themselves ; they lead either a solitary or 
a social life. Here we have examples of Saletta, Sabellaria, Ser- 
