Chap. U. AURELIA FLAVIDULA. 41 



They have a single wall, which is continuous with the outer wall of the tentacle 

 (PI. XI*. F/ffs. 3 and 9 P), and also with the single wall of the veil («) and with the 

 upper wall {Fit/. 9 i^) of the disk. The tentacle {Fiffs. 3, 4, and 9 i^) is about 

 three times as long as its basal breadth, and tapers to a rounded point; the inner 

 wall is hollow to the very tip, and is in open connection with the radiating canal (e). 

 In order to give a better understanding of the relation of all these parts just 

 described, we have made a longitudinal section of the veil, tentacle, and margin 

 of the disk, which can be readily understood by reference to the general lettering 

 at the head of the description of PI. XI. The lappets {Fiff. 4 /) of the oculiferous 

 lobes have a lancet pointed termination, and are remarkable for a median ridge 

 (/, and Fiff. 12 / f), which extends along the under side, a Httle exterior to the 

 median line, from the apex to the base, and thence, a little nearer the margin of 

 the lobe (j), to the circular canal. On each side of the ridge the surface is 

 concave, as a sectional view {Fiff. 12) shows. The upper side (/■*) is convex. 



The Eye.^ This is perhaps the most appropriate period of its life at which 

 the eye of Aurelia can best be studied, in all its details, when it is neither too 

 young to lack any of its characteristics, nor too old and grown opaque by the 

 development of dark pigment masses in its walls. The peduncle (PI. XP. Fiffs. 

 7 and 15 h to h^) has a peculiar oblong cylindrical shape, which is broader side- 

 ways {Fiff. 7) than vertically {Fiff. 15). In the first aspect it is rather elongate 

 ovate than otherwise, with the greater breadth at the base {Fiff. 7 h'^), whereas 

 in profile {Fiff. 15) it has the outlines and position of a finger half closed; but 

 even in this it varies considerably; at one time tlie end is perfectly round {Fiff. 8), 

 and at another is more or less pointed {Fiff. 15) or compressed. Its usual position 

 is indicative of its office, being turned upwards {Fiff. 15) between the lappets of 

 the lobe, and projecting to a greater or less extent above the edge of the disk; 

 but at times it is withdrawn under the lobe {Fiff. 4 h). There are two distinct 

 walls {Fiffs. 7, 8, and 15 h^ h^) to the pedmicle, and they are directly continuous 

 with the two walls of the lobe {f f) from which it arises, very much in the 

 same manner as the walls of the tentacle are continuous with those of the edge 

 of the disk; in fact, the eye peduncle is nothing more nor less than a solid ten- 

 tacular organ which hangs from the under side of the oculiferous lobe. The outer 

 wall {Fiffs. 7, 8, and 15 h^) does not differ in thickness from that of the lobe {f), 

 except at the end {h), where it thins out rather suddenly as it passes around 

 the tip; but the inner one {h^) varies in this respect according as it is seen in 



' Since I began the special study of the Aca- of these organs was furnished by Prof. II. J. Clark, 



lephs, I have always been inclined to consider the whose observations upon this subject are given at 



marginal bodies of their disk as ocular organs ; but full length and in his own words in the following 



the first direct demonstration of the true nature paragraph. 

 VOL. IV. 6 



