268 
RESPIRATORY ORGANS OF AQUATIC ANIMALS. 
around the head alone, and spread out widely into the sem¬ 
blance of a flower. In the Nereis (fig. 52) and its allies, they 
are set upon nearly every 
division of the body, and are 
much smaller. Their usual 
arrangement in these marine 
worms may be seen in fig. 
146, which represents one 
of the appendages of Eunice. 
The tuft of gills is shown 
at b ] at c is seen a bristle¬ 
shaped filament, which may 
perhaps be regarded as the 
rudiment of a leg ; and the 
projections to which the 
letters t and ci point, also 
seem connected with the 
movements of the animal. 
In the Arenicola (the lob¬ 
worm of fishermen) we find 
the respiratory tufts dis¬ 
posed on certain segments 
only, and possessing more of an arborescent (tree¬ 
like) form (fig. 147). 
315. A somewhat similar 
arrangement is seen in the 
larvae of many aquatic In¬ 
sects, which breathe by 
means of gills ; although all 
perfect Insects breathe air 
in the manner to be pre¬ 
sently described. In fig. 
148 is represented the larva 
of the Ephemera (Day-fly), 
which breathes by means 
of a series of gill-tufts disposed along the abdomen, 
and also prolonged as a tail. In the Crustacea, we usually 
find the gills presenting the form of flattened leaves or plates. 
In the lower tribes of the class, they project from the surface 
of the body; but in the higher, they are inclosed within 
a cavity, through which a stream of water is made con- 
Fig. 145. 
Gill-tufts of Serpula. 
Gill-tuft of Eunice. 
