4 DISCOPHORyE. Part III. 



Eschsclioltz has founded his subdivisions of the Phanerocarpae and Cryptocarpte, truly 

 marks the limit between the primary subdivisions which ought to be admitted 

 among the Discophorae. 



In the first j)lace, the marginal veil exists in some of the Acraspeda of Gegen- 

 baur, as well as in his Craspedota : it is, for instance, well developed in the Medusa, 

 or Aurelia aurita, the most common of all the European Discophorte, and has 

 already been described and figured by Ehrenberg in his elaborate paper upon that 

 species. I have also found it in another species of the same genus, Aurelia flavi- 

 dula Per. and Lc8., Avhich is quite as common upon the Atlantic coast of North 

 America, as the Aurelia aurita is along the shores of Europe. As to the position 

 and structure of the eyes in Discophorae, there is in that I'espect no essential 

 difference among them upon which a primary subdivision may be founded ; and 

 Gegenbaur, who has paid special attention to these organs, has already been led 

 to discard them as a test of their closer affinities. Indeed, while these organs are 

 altogether wanting in some of the Gymnophthalmata, others of the same division 

 have quite as highly organized eyes as some of the Steganophthalmata ; and as to 

 the difference in their position, it is not essentially modified by the folds of the 

 marginal disk which generally protect them, and these folds are also wanting in 

 some of them. Moreover, all the marginal organs of the Discophorse — those which 

 have been described as eyes as well as those which are considei-ed as auditive 

 sacs — are either simple or modified tentacles, and therefore strictly homologous with 

 one another, so much so that the differences which exist among them constitute, 

 in my opinion, only generic differences, as the modificatioiis, number, and position 

 of the tentacles themselves, and can in no way be made the basis of a primary 

 subdivision, as Forbes maintained. 



The distinction mtroduced by Eschsclioltz seems to me of higher importance, 

 though the manner in which he has expressed the differences he perceived does 

 not seem to have impressed other naturalists very forcilsly ; for all those who have 

 made a special study of the Acalephs since his time have discarded the characters 

 upon which he subdivided the Discophorae into Phanerocarpa; and Cryptocarpse, and 

 even gone so far as to consider the distinction as erroneous. It is true, Esch- 

 sclioltz did not know how the Cryptocarpse are reproduced: he did not even observe 

 their sexual organs, and therefore united them together under that nanie. But 

 the discovery of ovaries and spermaries in the majority of the CryptocarpsB did 

 not increase the resemblance of their reproductive organs to those of the Phanero- 

 carpae beyond what it really is: it only showed, that, like these, they also have 

 organs of the sexes. Had not the discovery of their presence obliterated the dis- 

 tinction made by Eschscholtz, it would have been remembered that in the Phane- 

 rocarpce the ovaries as Avell as the spermaries are complicated organs, contained in 



