1883.] The Siphonophores. 841 
Eudoxia. From the base of this polypite there ~ a tentacle 
(i) which has many side branches, 
each of which bears a simple 
pendant knob. The whole ten- 
tacle with lateral branches is 
easily retracted under the hel- 
met-shaped covering scale, as is 
shown in Fig. 6. As the Eudoxia 
separates from the Diphyes and 
leads an independent existence, 
so the heimet-shaped members 
Pre he 4 Praya cym- 
Dial (a Ch.) L 6, sexual 
bell; e, polypite; z, rinzai retracted, 
of the Praya colony separate from with tentacular kno bs; //, somatocyst ; 
y- 
l haped bod 
it, and after subsequent growth oat 
assume a very different shape from that which they have when 
attached. Although it is not yet known what the ultimate con- 
dition of the separated fragment is, there is probably no doubt 
that it later acquires a very different form as it grows older. 
There are two well-marked species of Praya found in the Med- 
iterranean sea, which are known as P. cymbiformis Leuck., and P. 
diphyes KOll.; they differ from each other in the relative size and 
shape of the swimming-bells and in a character already pointed 
out of the absence or presence of somatocysts in the posterior 
bell. In still a third species from the Bay of Villa Franca in 
Provence, we find the different attached diphyizodids so closely 
crowded together that they touch each other side by side along 
the length of the stem. This species, Praya gracilis F., is smaller 
than the others, has swimming-bells of a different shape and the 
openings into the bell cavity are larger and open more on the 
sides than in the above species. 
One of the most interesting genera of floatless Siphonophores 
is a genus called Gleba or Hippopodius, which is very common 
in the Mediterranean. This genus is placed by many writers on 
these medusæ among the Diphyz, but its many differences from 
the other genera are so great that it should probably be made 
the type of a new group equal in rank to the Physophore and 
Diphyz. The Siphonophorz! will then be divided into three 
l Exclusive of Velella (Rataria) and Porpita, aberrant genera which have few 
likenesses with the true Siphonophores and which are called Discoidex, These 
medusz are more closely related to floating hydroids than to medusæ with attached - 
