i28i Prof. H. J. Clark on Lucernaria. 



comparatively stiff and hydroidal tentacles, evidently indicating 

 a typical affinity to the fixed hydroid generation of the Sarsice, 

 BougainvillicB, Steenstrupice, &c. The simple, almost unilocular 

 chymiferous system is hardly more medusoidal, as regards the 

 multiplicity of its subdivisions, than in some of the Tubularians, 

 such as Tubularia and Corymorpha, which are described in Pro- 

 fessor Agassiz's fourth volume of his ' Contributions/ In con- 

 nexion with the hydroid form of Lucernaria, I would also men- 

 tion the total absence of a veil. This might, at first thought, 

 appear to furnish an argument in favour of the high relations of 

 this genus; but 1 think it is to be deemed one of the signs of 

 its inferior connexions. However, let us look at the progress 

 of velar development. In the ephydra state of all Steganoph- 

 thalmata, the veil is at one time greatly preponderant, when 

 compared with the size of the whole individual; but with 

 growth it gradually becomes less conspicuous, and finally, in 

 some adult genera of this order, it remains as a mere trace of 

 a veil, or, as in Cyanea and some Rhizostomidje, it is altogether 

 obscured. Now, it is noteworthy that among the lowest of this 

 order, such as Pelagia, we have a strong resemblance to the 

 ephydra state, and the ephydroid tongue-like veil is quite promi- 

 nent; and in Chrysaora it is hardly less so : ascending the scale, 

 we find it more inconspicuous in Aurelia, and still more so 

 in Cassiopeia, and, finally, altogether absent in Cyanea^, the 

 highest, in my opinion, of all the Steganophthalinata. Now, 

 one might suppose Lucernaria, m respect to the veil, to be in the 

 same category with Cyanea, which has resorbed its veil; this, 

 however, is not the case ; for, as I know from the study of the 

 younger stages of Lucernaria that it never passes through the 

 veiled phase, it falls short in its development as regards this 

 particular feature of Acalephan morphology. We must take 

 into consideration, also, the eyes, which are found to be as low 

 in point of structure as the merest pigment eye-spot of the 

 Gymnophthalmata. 



* The eplijdra-like appearance of Cyanea is illusory : the lobes about 

 the eyes comprise not only the original ocular lappets, but also a part of 

 the tentacular margin ; in fact, one-half of each margin on each side of an 

 eye is continuous with the ocular lappet adjacent. The tentacular margin 

 being incurved toward the centre of the disk, the veil must be still further 

 inward, and very probably the margin of the muscular bands corresponds 

 to it, the two merging into each other. The wide lacunar character of the 

 radiating canals is not a feature of inferiority, as might appear, but repre- 

 sents a continuation of the tendency (as may be seen in the progressive 

 stages of growth of Aurelia) to channel out the whole breadth of the disk, 

 until it finally becomes a simple cavitj'. In Rhizostoma, Stomolphus, and 

 Polyclonia the channeling is less carried out than in Cyanea; in fact, the 

 former is but a little beyond Aurelia in this respect. 



