130 D1SC0PH0R.E. Part III. 



aud while, at an earlier period, there are only eight of them corresponding to the 

 ocular lobes, there are sixteen in the next stage, the new set alternating with the 

 ocular lobes and corresponding to the tentacular pouches, which, even in Aurelia, 

 appear for a time like flat pouches (Pis. XP. Fig. 20, and XP. Fig. 4), and not 

 like chymiferous tubes. In Fig. 12, PI. XII., the tentacular pouches («) are just 

 beginning to project between the basal pai-t of the ocular pouches, but there is 

 not yet any trace of tentacles. The mouth has become a quadrangular aperture 

 {Fig. 12, c), projecting somewhat like a quadrangular funnel {Figs. 13 and 14), in 

 which the angles of the mouth project but slightly, aud do not yet show the 

 slightest sign of their later elongation into four slender pendant arms. In this 

 condition, the mouth of Pelagia corresponds to that of Aurelia as shown in PI. 

 XP. Figs. 18 and 28. The development of the genital organs seems to be more 

 tardy in Pelagia than in Aurelia, for our most advanced ephyra of Pelagia (PI. 

 XII. Fig. 12) shows no signs of them. The eyes present a conical tube, with 

 a round faceted termination. 



The condition of the young Pelagia here described resembles so closely the 

 structure of the small Medusae from the Mediterranean, described under the name 

 of Octogonia by J. Miiller, and under that of Nausithoe by Kiilliker and Gegen- 

 baur, that I have hardly any doubt that these Medusae are only undeveloped 

 specimens of the Pelagia noctiluca of the Mediterranean, in that state of growth 

 which would naturally follow immediately the one represented in my Fig. 12, PI. XII., 

 in which the tentacles and genital organs would begin to make their appearance. 

 It is true, Gegenbaur states that with these Nausithoe he found also the 3'oung of 

 Pelagia, but he may have considered as Pelagiae those only which already showed 

 the character of that genus, and referred their earlier condition to the genus Nausi- 

 thoe. At all events, if they differ, it is much to be regi-etted that he has not 

 pointed out the difference between the two, and has allowed an opportunity to 

 escape of establishing, beyond the possibility of a question, the generic difference 

 between the young of Nausithoe and Pelagia. 



