184 
THREE CRUISES OF THE “ BLAKE." 
Fig. 92. —Pterophysa grandis. үу. (Fewkes.) 
different levels in the jar in which it was kept. 
in great numbers, forming regular windrows, and, when dry, are 
blown by the winds to the highest parts of 
the beach. 
Some of the structural features of the 
Porpitide indicate affinities with acalephian 
JS corals like the Milleporidie, which date back 
to the cretaceous, but their general homo- 
logies ally them most closely with the tu- 
bularian hydroids of to-day. Among the 
finest siphonophores is a large Stephanomia, 
with its bells arranged in many vertical 
rows. 
One of the most interesting siphono- 
phores is Ptlerophysa grandis. (Fig. 92.) 
Of this species, which grows to a large 
size, huge specimens measuring no less than 
thirty feet, often came up on our dredge- 
wire in the Gulf of Mexico and the Carib- 
bean. It is closely allied to those which 
> oN Studer, the. naturalist 
of the “Gazelle,” re- 
gards as strictly deep- 
sea siphonophores. The 
9777 w polypite of large speci- 
E ~~ mens often measured 
ss 1 two to three inches. 
С^ Pterophysa and other 
siphonophores have the 
power of sinking and 
then swimming back to 
the surface, but neither 
Velella nor Porpita ap- 
pears capable of such 
movements. А very 
young Physalia, col- 
lected at the Tortugas, 
was observed to swim at 
