620 The Siphonophores. [ September, 
best to place under it a deep glass jar and then allow the water to 
flow gently into the vessel, floating with it the unconscious 
Agalma. Confined in a jar with the light thrown upon it ata 
proper angle, the animal may be studied at leisure through the 
sides of the glass. The observer must not forget that he can sel- 
dom keep these fragile jelly fishes alive, in confinement, longer 
than a few days. At first sight the multiplicity of parts in the 
Agalma gives usa rather confused idea of the structure of the 
several members which go to make up the colony. A more 
attentive study will reveal the fact that many of the component 
parts are frequently duplicated, and that five or six characteristic 
forms include those of all the appendages to an axis or stem 
which seems at times to give support to hundreds of differently 
shaped parts. Many of the appendages seem to be very different 
from these typical members, from the fact that they are in unde- 
veloped stages of growth. 
The general characters of the appendages I will consider in 
sequence after a mention of that part which connects all the dif 
ferent members, viz: the axis or stem. 
The Axis or Stem—A study of the anatomy of Agalma leads 
us naturally to begin with the rosy-colored axis. To this struc- 
ture the order of Siphonophore, to which Agalma belongs, owes 
its name. Passing through the colony from one end to the other, 
it connects all the individual members both physiologically and 
anatomically. Physiologically in the sense that to some of these 
rs falls the task of eating for the whole, to others the 
function of propulsion, while to a single individual is delegated 
the duty of floating the whole community.! If those individuals 
which serve the function of propulsion are detached, the colony 
has only passive means of locomotion. If the eating individuals 
are cut off, the colony dies for want of nourishment. New indi- 
viduals, however, are continually being developed from buds, so 
that it seldom happens, even when the stem is deprived of its 
members, that the colony suffers any fatal consequences. 
The length of the stem in larger specimens, when extended, is 
about four feet, yet the animal is often contracted to half that 
length. The diameter is about that of a knitting needle, and is 
nearly uniform ; a slight increase may be detected at either end. 
1 That which 7 sapport the animal in the water, and which is called the float, is 
considered by many naturalists a distinct individual. Ir regard it an organ and nọ 
an individual, Me reasons will be given when I consider the development of this 
structure 
