. 834 The Siphonophores. [ August, 
Monophyes! have, like Diphyes, two swimming-bells or necto- 
calyces. The most apparent difference in external shape between 
the genera which compose the group lies in the modification in 
size and shape of one or the other of these structures. 
The genus of Diphyz which resembles Diphyes most closely 
is known as Galeolaria (Epibulia). By many writers on these 
animals, instead of being regarded another genus it is simply 
called a species of Diphyes. It is larger, however, than the lat- 
ter, and capable of very rapid motion, darting hither and thither 
through the water, principally by the contractions of the poste- 
rior of its two swimming-bells. 
Galeolaria is widely distributed in the different seas, being very 
common in the Mediterranean. In American waters it has been 
taken off the Florida Keys in the Gulf Stream near Nantucket 
and is likewise recorded as far north as the latitudes of Green- 
lan 
The variation in the shape of their swimming-bells is one of 
the most prominent differences between it and Diphyes. While 
in both genera these structures are two in number in Galeolaria 
aurantiaca Vogt, both are much larger than in our common 
Diphyes, D. formosa F. The anterior swimming-bell of the for- 
mer genus is less conical in shape than that of the latter and as 
far as external appearance goes seems less perfectly adapted to 
rapid progress through the water. The part of the a 
animal as it forces its way along in the direction in which tt 
swims. While, however, it is the anterior end of the bell as t 
moves forward, it is not homologous to the apex of other medusa 
bells, but is morphologically one side of such a bell, or one wall 
which has become very much thickened and modified in such a 
manner that in its sidelong motion it may encounter the least 
resistance from the surrounding water. : 
There are deep-seated internal differences between the anterior 
of the two nectocalyces in the genera Diphyes and Galeolar 
1 The same is true, according to Chun, in Muggiæa. Specimens of a Da y 
but one nectocalyx are very common in Bermuda and Tortugas. I had a 
