Chap. III. ACTINAL SYSTEM OF CYANEA. 101 



of the lowei- floor is attached to the upper floor along the crooked lines ; but it 

 may not be superfluous to add, that in proportion as Cyanea grows older, the 

 gelatinous mass wliieh forms these ridges, grows not only wider, but also more 

 prominent, and isolates the different fields of folds more completely from one 

 another, as seen in PI. V". Fkj. 12 /-. These prominent ridges of the crooked 

 lines are best seen in transverse sections, as in Fig. 4, between e and c', and in 

 Fig. 5, between c and a. In PI. IV. Fig. 1, the ridges have barely begun to be 

 visible at the lower surface, and in Fig. 2 of the same plate they are not yet 

 ajjparent. 



The most prominent difference between the tentacles of Cyanea and Aurelia, 

 consists not only in the difference of their position, but also in the nature of their 

 connection with the main cavity of the body. In Aurelia, the tentacles commu- 

 nicate indirectly with the main cavity through the marginal circular tube ; Avhile 

 in Cyanea, they communicate directly with the wide pouches, which open freely 

 into the central cavity of which they are in reality only radiating prolongations. 

 This constitutes, unquestionably, another distinctive fiimily character of the Cyanida?, 

 as the tentacles of this genus are not strictly homologous with those of Aurelia ; 

 while the eyes, which are modified tentacles, are truly homologous with those of 

 Aurelia. The tentacles themselves are more comi^licated in Cyanea than in Aurelia ; 

 they are far larger in proportion to the size of the animal, and much more diver- 

 sified among themselves, as a mere glance at PI. III. may show. Their power of 

 contraction and expansion is truly wonderful, and the changes they undergo are 

 quite surprising. When fully expanded to the utmost limit of their capability, 

 they appear like mere threads of a uniform thickness for their whole length. 

 When retracted they thicken at the places which are most contracted, and this 

 thickening is in proportion to the degree of contraction. The extremity, how- 

 ever, is generally the most swollen part, though occasionally several swellings may 

 be noticed along the length of one and the same tentacle, while it is drawing 

 in. When the contraction takes place regularly, from the tip towards the base, 

 they may appear like large clubs suspended to a thin thread. I cannot suppress 

 my admiration for the skill with which Mr. Sonrel has reproduced all these ten- 

 tacles in their wonderful entanglement, and yet with such distinctness, that everj^ 

 one may be traced in unbroken continuity, from its point of attachment to the 

 furthest distance to which it stretches. He has succeeded in giving them all the 

 variety of aspect which they present in active motion, when in the same bunch 

 some of the tentacles may be entirely drawn in to within a fraction of an inch 

 of their point of attachment, and others stretched to their utmost length, while 

 others, again, wave from one bunch across the other bunches, or flow in undulating 

 lines, or bend upon themselves, or are twisted in a spiral, and still others appear 



