AGASSIZ. NATURAL HISTORY OP THE UNITED STATES. 349 
a minute sac, tlie prismatic contents of which, unlike the concretions 
of the Gymnophthalmata , are not soluble in acetic acid. These 
4 lithocysts ’ may or may not he furnished with pigment-spots ,* and 
their protection by hoods, though frequent, is not invariable. Lastly, 
within the central cavity, in the neighbourhood of the reproductive 
organs, are situated groups of peculiar solid filaments, the ‘ generative 
(or gastric) tentacles,’ not, as yet, noted in the lower Medusce. 
We agree, therefore, with Professor A gassiz when he states “that 
neither the presence nor the absence of a veil around the margin of 
their disk, upon which Gegenbaur has based his division of the Cras- 
pedota and Acraspeda, neither the exposed nor the protected posi¬ 
tion of the marginal eye-specks, which Forbes took as a basis for 
the separation of the Steganophthalmata and Gymnophthalmata, 
nor the development of the ovaries and spermaries, upon which 
Eschscholtz founded his sub-divisions of the Phanerocarpae and 
Cryptocarpae truly mark the limit between the primary subdivi¬ 
sions which ought to be admitted among the Eiscophorae.” And 
we think that he has rightly directed prominent attention to the 
very different relations of their reproductive organs. “Had not the 
discovery of their presence obliterated the distinction made by 
Eschscholtz, it would have been remembered that in the Phanero- 
carpae the ovaries as well as the spermaries are complicated organs, 
contained in distinct pouches communicating directly with the main 
cavity of the body and discharging their eggs into that cavity and 
then through the mouth; while in the Cryptocarpae they consist 
only of folds along the course of the chymiferous tubes or upon the 
sides of the proboscis, and discharging their eggs immediately into 
the surrounding medium, but never through the main cavity and the 
mouth.” But,though looking on this structural distinction as one of 
ordinal value, he is by no means disposed to exaggerate it, for, as he 
reminds us in the closing paragraph of his first section, there is “ the 
closest homology ” between the reproductive organs of both groups, 
“ for the large pouches containing the ovaries and spermaries of the 
Phanerocarpae are, after all, only dilatations of the chymiferous 
system along the course of its radiating channels ; while in Crypto¬ 
carpae, instead of large pouches there are simple, narrow tubes, upon 
the sides of which the eggs are developed, and from which they 
immediately drop into the surrounding medium. The fact, that in 
some Cryptocarpae the eggs are developed upon the proboscis, in no 
way conflicts with this explanation, since the angles of the proboscis, 
as may best be seen in Bougainvillea , are quite as much the direct 
prolongation of the radiating tubes, as the ovarian pouches of 
Cyancea are a direct prolongation of its radiating chymiferous sacs.” 
* The Oceania turrit a of Forbes, cited by Gegenbaur (op. s. cit.) as the only 
example of a Naked-eyed Medusa in which vesicles and pigment-spots co-exist, has 
both kinds of these bodies situate at the bases of the four tentacles, between each 
pair of which are “three yellowish marginal tubercles, with rudimentary ocelli.”’ 
This species does not appear to have been examined since Forbes first discovered 
in 1845. See his Monograph, p. 28. 
