1883] - The Siphonophores. 837 
function of this groove and its cover, the thin plate which has 
en mentioned, is to form a receptacle into which the retracted 
stem and its attached members can be wholly or partially with- 
drawn. The modification in the form of the bell, resulting from 
the formation of the groove and its cover, gives rise to a compli- 
cation in the course of the radial canals in the bell walls. While 
three of these tubes have a normal course extending directly 
from a common origin to the bell margin ; a fourth which lies on 
the same side as the groove or external canal and its cover, is 
somewhat modified. It starts from a common union with the 
others, but instead of passing directly to the bell margin divides 
midway in its course into two branches. One of these branches 
ends blindly in the bell walls a short distance from the bifurca- 
tion, while the other after a tortuous course eventually ends in the 
immediate vicinity of the bell margin? 
The diphyizodid of Abyla (Figs. 2, 3, 4) closely resemble 
those of Diphyes in many particulars. The covering scale (cs) 
is, however, polygonal in shape instead of hemispherical, and 
almost its whole interior is taken up by a large somatocyst (s). 
The swimming-bell, clusters of male and female sexual bells, 
tentacle and polypite are similar to those of Eudoxia. 
The diphyizodid of Abyla, like that of Diphyes, was formerly 
described as a genus widely different from that to which it is now 
known to belong. Historically it is interesting from the fact that 
from a study of its anatomy and growth the true nature of the 
diphyizodid in general was recognized. 
The reduction in size in the bell of Abyla has gone so far in a 
genus called Monophyes that the anterior bell is missing and we 
find a single swimming-bell which has resemblances to both the 
anterior and the posterior nectocalyces of the genera which have 
already been described. 
The single swimming-bell of Monophyes has a baba 
shape and is without ridges on its external surface. On one side 
of the bell walls there is an enclosed canal out of the opening 
into which hangs the axis. The axis or stem can be withdrawn 
into the canal where, when retracted, it is securely packed in the 
Same way that a like organ of Abyla is placed in the groove 
‘A blindly ending tube also arises from the point of union of a radial and circu- 
pini and extends to the neighborhood of the plate which has been described 
