130 MARINE INVERTEBRATES 
ORDER, SIPHONOPHORA 
FREE-SWIMMING 
COLONIES 
This order of hydroids consists of free-floating communities 
and is one of peculiar interest, since it shows in a clear manner 
the special function of each individual member of the colony, 
and illustrates better than the foregoing, perhaps, the curious 
forms of animal life which this class presents. 
Genus Nanomia 
N. cara. This species is found on the New England coast. The 
members of the community are arranged along a hollow stem about three 
Adult Nanomia cara, 
inches long which opens into 
every individual. At the top 
of the stem is a sae, or float; 
just below this is a group of 
swimming-bells which have 
no manubrium or mouth, and 
whose sole function is to pro- 
vide locomotion for the com- 
munity; and below these are 
three sets of zodids, each 
having a triangular shield 
and tentacles. The tentacles 
are longer than the main stem. 
One of these last groups con- 
sists of the nutritive members, 
the mouths of the community, 
resembling manubriums of 
swimming-bells out of place. 
Each one has at the point of 
attachment a bunch of long, 
delicate tentacles having pen- 
dent knobs of lasso-cells. A 
second group, also with 
mouths, has shorter tentacles 
which are carried in spiral 
coils. The members of the 
third group have but one ten- 
tacle each and resemble the 
float at the end of the stem; 
presumably these drop off and 
produce new colonies. There 
are also on the lower part of 
the stem other reproductive 
members, which resemble the 
clusters of buds seen on 
