AGASSIZ. NATURAL HISTORY OF THE UNITED STATES. 
V \ . 
into a group* by themselves, morphologically equivalent to the 
Phanerocarpce, and intermediate between them and the lower 
Medusce (with their Hydroid allies). The members of such a group 
would at least agree: (1) in their lateral reproductive pouches ; (2) in 
their dorsally furrowed bell, with its tentacles remote from the 
margin; and (3) in the absence of a circular vessel. But the posi¬ 
tion of their reproductive organs, though intermediate, in some 
degree, between what we find in the two sections of Discophorce, 
Eschsch., respectively, approximates these forms more nearly to 
the higher Medusa, among which, likewise, their much modified 
canal system, and particularly the absence of a circular vessel may 
be paralleled. On the other hand, in all Cryptocarpce this vessel 
occurs, and communicates with the central cavity by narrow radia¬ 
ting canals. In the Cryptocarpce , also, the tentacles, when present, 
are strictly marginal, but it is otherwise with many of the higher 
Medusce. Even Eritz Muller himself acknowledges that the Charyb¬ 
deidce are more closely related to the latter than to the former, and 
that, if the old binary division of Discoid Medusa be retained, “ the 
Charybdeidce can only find their place among the higher Discophorce, 
with which they have in common at least the gastric filaments and 
the insoluble contents of the marginal bodies.” 
Thus, with reference to the systematic position of the two 
families in question, four separate opinions have been held, viz.:— 
1. That of Eschscholtz, who refers both to his Cryptocarpce. 
2. That of Agassiz, who places both with the Phanerocarpce. 
3. That of Gregenbaur, who transfers the Charybdeidce to the 
Phanerocarpce , leaving the JEginidce with the lower Medusce. 
4. That of Eritz Muller, who unites both families into one group, 
intermediate between the Hydroid Medusce and Phanerocarpce. 
* Eritz Muller’s entire arrangement is as follows : — 
HYDROMEDUSiE. 
1. Siphonophora, together with their free reproductive zooids. 
2. Hydroida. 
a. Tubular bm, and the Hydroid Medusae without organs of sense or with 
eye-specks. 
b. Sertnlarina , and the Hydroid Medusae with marginal vesicles. 
In relation to development this group includes : 
a) Polypites without free reproductive zooids. 
(5) Polypites with free reproductive zooids. 
y) Free sexual animals without polypites, (Trachynema, Liriope). 
3. Acalepeue, R. Lt. (Discophoree Phanerocarpae, Eschsch.). 
a. Monostome (Medusidae, Esehsch.). 
b. Polystome (Rhizostomidae, Eschsch.). 
4. jEginoida (ASginese, Liitk.). 
a. Lower. Cunina (iEgina rosea, Eschsch.); iEgineta ; Polyxenia ; JEgi- 
nopsis bitentaculata. 
b. Higher, Charybdeidce. JEginopsis Laurentii (?) ; JEgina (citrea); 
Charybdea (marsupialis); Tamoya; Periphylla (Ch. periphylla, Per.). 
Save in its recognition of the “ TEginoida ” as a primary division, this classi¬ 
fication of the Hydromedusce closely agrees with that of R. Leuckart. 
