222, BULLETIN OF THE 
arate Nanomia from the allied Stephanomia, auct., Halistemma, Claus, and 
Agalmopsis, Fewkes. We have on the Florida coast an Agalmopsis, A. fragile, 
Fewkes, which has the same knot as Nanomia, and in other particulars is very 
near it. They are not the same species, although generically they seem to be 
very close. For the present I adopt Agassiz’s name, Nanomia, not because it 
differs from other Siphonophores in the way some have thought, but on new 
grounds, or because of the marked character of the ‘‘ oil globule” in the taster 
of Nanomia. In all other respects Nanomia is like Agalmopsis, Fewkes, from 
the Mediterranean and Floridan Seas. 
It is predicted that the egg of Nanomia will be found to develop at first a 
float, and then an embryonic tentacle with embryonic knobs ; that there is 
never developed a primitive hydrophyllium ; and that an Athorybia-like cov- 
ering scale does not form. The type of development, as compared with that of 
Agalma, is more abbreviated, and consequently more direct in Agalmopsis 
than in Nanomia. 
The facts which lead to this conclusion may be seen from what is said below. 
The state of our present knowledge of the development or growth of the lar- 
val stages of Nanomia may be shown in the following historical summary : — 
1. The larva in which the float is fully formed is traced from older larvee 
into the genus Nanomia. This series of observations was made by A. Agassiz, 
the discoverer of Nanomia, who considers that the youngest stage (with float 
only) develops from a bud, and also from the egg. The earliest stage 
which he figures he regards as identical, whether formed by either method of 
development. 
2. Metschnikoff obtained younger stages, or those before the fluat is devel- 
oped, cf an allied Physophore. The youngest stage which he figures is a 
planula. 
3. The author here describes the segmentation of the egg of Nanomia into 
the eight-cell stage. 
The only break now in a consecutive series of observations is between two 
and three, or the eight-cell stage and the planula. Judging from what we 
know of other Siphonophores, no embryonic structures appear in this gap, and 
we are justified in supposing that no primitive hydrophyllium, or covering 
scale, appears before the float in Nanomia. 
The fact that in Nanomia no primitive hydrophyllium, such as is found in 
Agalma, exists, does not prevent our recognizing in the youngest larva with a 
float, and a tentacle with embryonic knobs, all the parts of the stage called 
the primitive larva. Metschnikoff has shown that a Siphonophore float is 
homologous to a bell,* and I have no hesitation in accepting the theory that 
the float of Physophores is homologous with one of the nectocalyces of the 
* The primitive larva, or, as I have elsewhere called it, the primitive medusa, 
from which all the Siphonophores have phylogenetically arisen, would seem to be 
somewhat like older stages on Plate III. of my “ Development of Agalma,” Bull. 
Mus. Comp. Zool., Vol. XI. No. 11. 
