Chap. IV. PELAGIA CYANELLA. 129 



soon assumes an ephyra-like condition {Figs. 10 and 11). In Fig. 10, which repre- 

 sents it as swimming, b h indicate the lobes of the ephyra, which, in Fig. 11, are 

 seen stretched on a plane, and disclosing the terminal emarginations, between which 

 arise the eyes; h marks the termination of the radiating ^jouches, and a the mouth. 

 We have thus a direct and gradual transition from embryos similar to a scypho- 

 stoma which has not yet got tentacles. Fig. 7, to one which has seeming tentacles, 

 Figs. 8 and 9, eight in number, and which, instead of developing into slender ten- 

 tacular appendages, are enlarged into lobes, corresponding to those of the ephyra 

 of Aurelia, as represented in PI. XP. Fig. 26, traversed by broad chymiferous pouches, 

 such as exist also in Aurelia (PI. XI''. Fig. 4) during the earlier stages of their 

 ephyra condition, showing that in this type the development takes place by a 

 gradual metamorphosis of the scyphostoma into an ephyra, without the intervening 

 strobila condition, and therefore without a multiplication of individuals from one 

 and the same egg. 



This direct transformation of the scyphostoma into the ephyra is important, not 

 only as exhibiting a special mode of development in the Pelagid*, when compared 

 to the Cyaneida3 and Aurelidaj, but also in a morphological point of view, since it 

 shows, beyond a question, that the radial prolongations of the body, which arise 

 on the actinal edge of the scyphostoma, may be developed into two different kinds 

 of organs in different types, becoming tentacles in Aurelida^ and Cyaneidje, by 

 direct metamorphosis, and becoming radiating pouches, with an eye in its radial pro- 

 longation in Cyaneidaj; thus showing, through embryological evidence, what I have 

 already maintained on other grounds, that the ocular apparatus is a tentacular appa- 

 ratus, and the eye a metamorphozed tentacle, or, in other words, that the tentacles 

 in Radiates are the lowest condition of that structural element which, in its highest 

 development, appears as an eye. Thus the pigmentation of a tentacle, near its 

 base, is the first indication of an approximation towards an eye, and the reduction 

 of the tentacular element is generally accompanied by a higher develojDment of 

 the ocular element. It has already been shown, also, that in abnormal states of 

 strobilas there are all possible transitions and combinations of both. See PI. XL 

 In the state of development represented Fig. 11, PI. XII., the radiating pouches 

 are simple, and extend only to the base of the eyes, in the emargination of the 

 eight lobes ; but within twenty-four hours such an ephyra passes into the condition 

 represented in Fig. 12, in which the radiating pouches have enlarged into marginal 

 sacs, on the two sides of each eye peduncle. In this stage the ejjhyra of Pelagia 

 closely resembles that of any Aurelia in which the veil and tentacles have not 

 yet begun to be developed, as represented on Plate XP. In that condition of 

 the Aurelia, the radiating prolongations of the chymiferous system are not yet closed 

 branching tubes, as in later periods, but flat pouches, as in Pelagia and Cyanea; 



VOL. IV. 17 



