776 The Siphonophores. [ October, 
mon in the Mediterranean, and found likewise in the Atlantic 
near the Cape Verde islands. It is one of the most beautiful and » 
graceful of all the group to which it belongs. 
Physophora differs from Agalma and from all other Physo- 
phoridz in this particular, that the polyp-stem to which is affixed 
polypites, covering-scales, tasters and sexual organs in Agalma, 
and which takes on the form of a long tube in this animal, becomes 
reduced in length in Physophora and inflated into a special bag, 
from the under side of which, in a definite spiral arrangement, 
structures similar to those of the polyp-stem in the Agalma, hang. 
It is precisely what would be expected if the portion of the axis 
of Agalma below the lowest nectocalyx were inflated into a Sac, 
and the appended structures drawn into a spiral line over its un- 
der surface. The nectocalyces and the nectostem do not essentially 
differ in the type and in Physophora. The peculiar tentacular 
‘pendants of this animal I will not consider at length, since an 
account of them would draw me into a description too technical 
for these papers. 
One genus of the Physophoride, closely related to the young 
of Agaima, remains yet to be mentioned. It will be remembered 
that we described the Agalma as passing through what was called 
an Athorybia stage. That form is permanently taken by the ge- 
nus Athorybia, from which it was named. The resemblance 
of the two ‘is, however, only a likeness in general shape, and is, in 
particulars, quite remote, for when we study the form of the cov- 
ering-scales, the tentacular pendants and the fine anatomy of the 
float, we find very little resemblance between the two. The term 
“ Athorybia stage” is a very convenient one to designate a well 
marked larval condition of the young even of other genera be- 
sides Agalma.,. 
In the genus Athorybia there are no nectocalyces, and if any 
axis is developed, it is so small as to be practically wanting. In 
place of swimming-bells, the covering-scales are capable of quite 
extended motion, and arise directly under the base of the float, 
thus forming a crown or circlet which encloses that body. To 
the outline and arrangement of these structures, as well as the 
complete absence of nectocalyces, Athorybia owes its peculiar 
shape. It is probably an arrested embryonic condition resembling 
closely the young of Agalma, although differing from it in struc — 
tural details. c 
