Prof. H. J. Clark on Lucernaria, 21 



tte Steganophthalmatan Medusse, and, moreover, in order that 

 I may not complicate matters, I will compare it, organ for 

 organ and part for part, with one of our most common Medusse, 

 Aurelia flavidula, Agassiz. The aboral side, which corresponds 

 to the so-called dorsal region of other Acalephse, projects at the 

 apex into a moderately long columnar body, usually called the 

 peduncle of Lucernaria. With the exception of the four equi- 

 distant channels and the four muscular cords which alternate 

 with them, the peduncle is a solid gelatiniform mass, covered 

 by the outer wall. This gelatiniform substance also constitutes 

 the bulk of the disk, filling the entire space between the outer 

 wall and the inner or lining wall of the digestive cavity, and 

 directly continuous with that in the peduncle. In Aurelia, 

 Cyanea, and other Acalephs, this substance appears like an 

 amorphous gelatiniform or semicartilaginous mass, with a few 

 irregular cells scattered here and there * ; but in Lucernaria it 

 Las a highly organic structure. Extremely elongate, columnar, 



* In June 1862, I made a careful study of the structure of the gelatini- 

 form substance oi Aurelia flavidula , Ag. There are two kinds of lilrt'o- 

 cellular bodies which pervade the gelatiniform layer. One kind are irre- 

 gular, dark, conspicuous cells, similar in appearance and size to those of 

 the outer wall of the aboral side, with from one to four or five jagged 

 caudate prolongations jn-ojecting in every direction. These are most 

 numerous next the aboral side of the disk, and departing from that region 

 they become less frequent as we appoach the oral side, at which place they 

 are very much scattered. The other kind of bodies are very faint, nucleated, 

 nodose fibres, and form a vast anastomosing network, which, like -the 

 darker, caudate cells, pervades the whole of the gelatiniform mass of the 

 body, from the aboral to the oral side. It resembles elastic tissue very 

 closely. Next the aboral side these fibres trend mostly parallel vTise" with 

 the outer wall, or at very oblique angles to it ; but, jjassing inwardlyjUliey 

 gradually assume a direction transverse to this, and then, anastotnCfeing 

 less frequently, they become in ap]iearance like slender parallel ct.<luinns, 

 based upon the double wall in which the chymiferous channels run. Between 

 the latter and the outer wall of the oral side the fibrous bodies are exces- 

 sively faint and less frequent, but still continue the trend which they have 

 on the aboral side of the double wall. The peculiarities of these two kinds 

 of bodies are fully described by Max Schultze (Ueber den Bau der Gallert- 

 scheibe der Medusen, Miill. Aichiv, 185G, p. 311, pi. 11, 12) from ol)serva- 

 tions which he made upon Medusa {Aurelia) aurita, Rhizostoma Cuvieri, 

 and R. Aldrovandi; but in all of them, he says, the fibres run in every 

 direction : " sie laufen gestreckt in alien Richtungen, theilen sich haufig 

 und verbinden sich unter einander unter alien moglichen Winkeln." Now, 

 in Medusa {Aurelia) aurita, which is very near, if not identical with, our 

 Aurelia flavidula, Ag., it is very jjrobable that these fibres are arranged as 

 in ours ; and yet I cannot see how Schultze could have overlooked this 

 arrangement. My observations were made upon perfectly fresh specimens, 

 and without the help of any reagents. In our Lucernarian, and, in fact, in 

 all the Lucernarice (see Journal Boston Nat. Hist. Soc, March 1863), the 

 fibrous bodies do not anastomose, but trend in direct lines, from the outer 

 to the inner wall. 



