Chap. II. STRUCTURE OF THE ADULT. • 59 



in color is very striking, and the distended ovaries and tlie marginal folds of the 

 arms filled with eggs, impart to the females a characteristic, yellowish appearance, 

 whence the name Aurelia tlavidula; though, at a later time, when the young begin 

 to develop, the yellowish tint passes into a more brownish-orange tint. The males, 

 on the contrary, have their spermaries more deeply jjurple before fecundation takes 

 place ; afterwards their genital organs assume a paler, more rose-colored tint, and 

 finally fade into dull white, the mai'ginal fringes of their oral appendages never 

 swelling, as they do in the females, in consequence of the enlargement of the young. 

 When the genital pouches begin to grow large, the inner peripheric margin of their 

 lower iloor gradually swells and projects into the genital sac, until a garland of folds 

 (PL VIII. Fl(j. 7), waving along the whole edge, is formed, in the plications of 

 which the ovarian and spermatic cells are developed, as seen in PI. VIII. Fig. 8, 

 and PI. IX. Figs. 1 and 2. Near the folds which contain the eggs and the sperm- 

 cells, hang the many rows of digitate appendages ali-eady described, which by the 

 time of the maturity of these organs are extremely numerous, and occupy a band 

 of about the same dimensions as the sexual organs themselves. The function of 

 these digitate organs is jDrobably to determine currents in the immediate vicinity 

 of the eggs, and thus to secure a constant supply of fresh, aerated water in their 

 immediate vicinity. 



There are marked differences in the parts along the margin of the disk between 

 the young and the adult. Not only are the tentacles growing more and more 

 numerous and proportionally longer, but the lobules which sepai\ate them are greatly 

 enlarged, so much so, that they apjiear like flat, broad lobes (PI. VII. Fig. 4), between 

 which the tentacles seem to arise as from sockets, Fig. 3, when seen from above ; 

 while the thickness of the lobules themselves is greater on their lower side, as 

 shown in Fig. 2, and from their inner and lower margin hangs the veil, as seen in 

 PI. VIII. Fig. bed. The character of the tentacles in the intervals between two 

 eyes is very uniform. As in earlier age, however, they are thicker at the base, 

 with a wider cavity tapering to a blunt end (Pis. VII. and VIII. Fig. 6), the cavity 

 extending nearly to the tip, Init gradually narrowing, while the outer surface ajipears 

 as if covered with beads, owing to the crowded clusters of lasso-cells with which 

 they are set ; near the eyes they are gradually smaller, so that the margins of 

 the indentations in which the peduncles of the eyes, with their visual lappets, are 

 situated, appear like free spaces, destitute of tentacles; and, indeed, there are here 

 no ordinary tentacles, but the margin of the disk assumes a peculiar appearance, as 

 in PI. IX. Fig. 4. The sockets for the tentacles are wider, and the lobules between 

 them flat and broad ; while the ocular apparatus itself may be considered as a 

 modified tentacular margin, the eye, with its peduncle, being a tentacle with a 

 specialized termination, and the lappets of the eye, so prominent, and comparatively 



