- 
1881. ] The Siphonophores. 781 
what we have already studied. The stem, half way between each 
cluster (7), is jointed so that as the animal grows, or the stem 
elongates, that cluster most distant from the float ruptures its con- 
nection with the colony at the joint in the axis, and when sepa- 
rated from the remainder, leads an independent life. It thus hap- 
pens that these little clusters are often found floating alone in the 
water, hanging from the fragment of the stem, having broken 
their connection with the parent, or rather with the colony, to 
which they were formerly attached. As is also the case in a lar- 
val stage of a common jelly-fish, Aurelia, known as the strobila, 
which is, however, attached at one extremity to the ground, suc- 
cessive terminal members continually separate from the collection 
and swimming away, develop into new Aurelie, so terminal clus- 
ters of the free-swimming Apolemia are successively broken off 
from the colony as it matures. The likeness between the method 
by which Aurelia and the clusters of Apolemia develop is mor- 
phologically very great. Let us consider the composition of a 
single cluster which has separated in this way from the colony, 
and see how far this likeness can be traced. 
The fragment of an Apolemia ruptured from the remainder of 
the colony, resembles closely in shape a number of transparent 
spheres fastened together by one pole, from which hang down a 
number of polyp-like organs. The cluster is, in the main, com- 
posed of many jelly-like bodies joined together on the fragment 
of the stem. These bodies are but modified covering-scales, and 
are generally penetrated by a’ single tube, just as is found univer- 
sally to be the case among other genera. The covering-scales 
are carried uppermost as the cluster floats in the water. From 
the lower side, and also attached to a segment of the axis, there 
hangs down the same flask-shaped feeding-polyps (/), which have 
been described in Agalma. The tentacles (c) of the feeding- 
Polyps do not bear pendants as are found in all the other Physo- 
Phores except Physalia. In each cluster of polyps there are two 
flask-like bodies, in general shape not different from the remain- 
ing, which have a bright red color. We are unable to assign 
any reason for this peculiar coloration in these two feeding- 
polyps. Lastly, in each cluster of the Apolemia colony we find 
Sexual-bells, male and female, which fill out the complement of 
©rgans necessary for the independent life of the cluster. 
On account of this independence of life in each cluster, when 
