Fewkes.} 294 [October 1, 
especially when the waters of our southern bays have been more 
carefully studied.+ 
In the course of my work in Villefranche sur Mer, my fisherman 
brought me five or six specimens of Rhizophysa filiformis. 1 think — 
the form is not common there, at least in the winter months. My 
specimens were taken in February and March. On account of its 
apparently mutilated condition, Rhisophysa is one of the most 
bizarre of the Siphonophores. This is mainly due to the fact that 
the bells, which fail among related forms in Physalia, are here com- 
pletely wanting. They neither appear as swimming organs, covering 
scales, nor in the so-called sexual parts. 
The float alone, that strangely modified structure eine Metschni- 
koff has homologized to a bell, and whose form is so varied, is the 
only thing which we find in Rhizophysa representing a medusa bell.” 
Except the most limited movements of contracting the axis, the 
animal is wholly devoid of means of progression. The contrast 
1 Up to the present time, there have been described from New England waters 
only three forms of Siphonophorae. Nanomia cara, the only known Physophorid 
except Physalia, was studied by Mr. Agassiz. It was found by him at Newport 
and Nahant. In the summer of 1876, while at work in his laboratory at Newport, 
I found a second physophorous Acaleph, Agalma elegans, as yet neither described 
nor figured. Of Calycophoridae none have yet been found in New England waters 
by others. To this fauna I can add Eudazxia Lessonii and Diplophysa inermis. 
Velella is sometimes washed up on our coasts, and Physalia is by no means so 
rarely met with in Vineyard Sound as in Villafranca, Naples or Messina. 
2The origin of the float has of late been studied in other Physophoridae by 
Haeckel, Kowalewsky and Metschnikoff. The opinion of the former that it is sim-~ 
ply one end of the primitive cavity seems, after the investigations of the two last, 
to be erroneous, Metschnikoff and Kowalewsky both showing that it first appears 
as a simple bud, independent of the eavity itself. Kowalewsky believes that the 
float is first formed as an invagination. In Metschnikoff’s figures of Agalmopsis 
Sarsii the float is represented as of ectoderm alone. Both ectoderm and entoderm 
enter into the formation of the bud, which is at first an invagination, as many of my 
own preparations show is the casein Physophora hydrostatica. The earliest stage of 
the young of Physophora is a true gastrula of the invaginate kind. The theory of 
the relation of the Siphonophorae to a budding Medusa and not to a free swimming 
hydroid was first suggested by McCrady. In late years it has been urged on em- 
bryological grounds by Metschnikoff and P. E. Miller. This theory is directly 
connected with the homology of the float. Homologicaily speaking there is very 
little difference between a free swimming hydroid and a medusa with attached and 
highly differentiated buds such as one finds them in the Siphonophorae. While 
Haeckel was the first to discover the resemblance of the larva of the Physophoridae 
to a young medusa and to homologize the provisional “deckstiick ’ with the bell of 
a medusa, he looks upon the other later formed bracts as individuals after Leuck- 
art’s conception. It is a strange inconsistency. 
