192 The Siphonophores. [ March, 
This body is not the end of the primitive tube enlarged, but is a 
true bud from it, and as such should be considered in all our 
studies of its homology. 
2. ATHORYBIA STAGE OF THE YOUNG AGALMA. 
As the primitive medusa grows older, the primitive covering 
scale is lost, either by absorption or by a rupture of the connection 
with the growing larva, and new buds take its place, forming a 
circlet of covering scales just under the float. These covering 
scales are different from those of an adult Aga/ma, and have their 
edges very finely serrated. They are in fact very similar in their 
structure to the covering scales of the genus Athorybia, and on 
— account the name of Athorybia stage, seems not inappropriate 
to apply to this condition of the growing 
Aga/ma. 
Another peculiarity of this stage is the 
character of the tentacles, and the knobs 
which hang as pendants from them. The 
tentacular knobs of the Athorybia stage 
| | never develop into an adult knob like 
| » Fig. 4. They are embryonic and are con- 
‘ hi fined to the young larva, more especially 
“yy to: that stage known as the Athorybia 
larva. On account of their restriction to 
larval conditions it may be well to speak of 
them as the larval knobs. They are club- 
shaped, oe pee peculiar cells at the distal end there arise 
structures which resemble stiff hairs. (Fig. 9.) 
a a 
oe cas orto 
SF || 
Fic. 9. mpeg larva of 
3. LARVA WHICH RESEMBLES THE ADULT. 
(PHYSOPHORA STAGE.) 
The Athorybia larva has no swimming bells and no elongated 
axis or stem, but immediately after that stage is reached an axis 
begins to form at the same time that buds, producing swimming- 
bells, make an appearance. A circlet of covering scales of very 
different outline and destitute of serrated edges, replace those 
which characterize the Athorybia larva. A new tentacle, with 
tentacular pendants like the adult, also make an appearance, so 
that we have a stage in which both kind of pendants, embryonic 
and adult, are to be seen. I have called this stage of the young 
Agalma the Physophora stage, because at the very end of the 
