1879.] 293 [Fewkes. 
of the so-called sexual clusters at the base of the polypite, and the 
entire absence of any of the three kinds of tentacular knobs, seem to 
point this out very evidently. It rarely happens in Rhizophysa that 
the tentacular knobs are dropped by long confinement in a glass 
vessel, so that one could hardly believe the specimen which he had 
was mutilated. The thread-like character of the secondary appen- 
dage to the tentacle would seem to indicate the truth of the theory 
that they were only pedicles of secondary appendages whose sacculus 
had dropped off. 
Huxley figures and describes the coeca-like appendages which are 
so well marked in the float of R. filiformis, and he declares himself 
unable to find the small rounded cells between the endoderm and 
the air sac. I was also unable to find these in my own specimens, 
a failure, I think, as such structures have been redescribed. Con- 
sidering the problematic position of Velella and Porpita these bodies 
have more or less theoretical importance. If one should push the 
comparison of a Velella to a physophorid as far as Leuckart has in 
his schematic figure, one could better compare that dark mass which 
has been likened to a liver in the case of Velella with the finger-like, 
often bifurcated appendages of the float in Rhizophysa. 
One of the best descriptions which we have of this animal is that 
by Gegenbaur. He observed it frequently in quiet weather in the 
neighborhood of Messina. I shall frequently have occasion to speak 
of his account. 
Kolliker does not appear to have studied the form. No mention 
of it occurs in his work on the Siphonophorae of Messina. Leuc- 
kart and Vogt did not find Rhizophysa in the bays near Nice. The 
former of these authors declares in a note that the Rhizophysa fili- 
formis of Risso is the same thing as the animal which he calls 
Galeolaria jfiliformis. Keferstein and Ehlers give a casual mention 
of it, supporting Sars’s view in regard to the tentacular knobs. 
One of the last additions to our knowledge of the different. Rhizo- 
physidae, is a paper by Studer (Zeitschrift fiir wiss. Zool., Bd. xxiv) 
on the Siphonophorae of the deep sea. Iam inclined to question 
the validity of the new genus and species which he proposes. That 
these animals were brought up from the depths which he gives is 
also, as Mr. Agassiz shows, not conclusive. Among the few forms as 
yet described as belonging to the Siphonophorae from North American 
waters, no mention has been made of Rhizophysa. ‘There is hardly 
a doubt that it will later be added to the number already known, 
