NERVOUS SYSTEM OP AURELIA AURITA. 
575 
of the monograph by the Brothers Hertwig,* in which the literature of the whole 
subject is treated of in an exhaustive manner, rendered superfluous any further action 
on my part. As to the work of the Brothers Hertwig it is difficult to do justice to 
the carefulness of the descriptions and illustrations, and the philosophical way in 
which the subject is treated. Unfortunately, their supply of Aurelia seems to have 
been limited, and altogether their observations upon the Acraspeda have been com- 
paratively few, although the types studied were well selected. This will probably 
account for the fact that the subumbrellar plexus which I have described in Aurelia 
has escaped their notice. Moreover, the nervous character of the epithelium of the 
fovese near the lithocysts is not alluded to by them, probably because in the acras- 
pedote species which they chiefly examined the epithelium of these parts has not so 
distinctly the character in question as it has in Aurelia. In Chrysaora hyoscella, for 
example, the ectoderm of the superior fovea; is throughout like that of the rest of the 
upper surface of the umbrella, t I had hoped to have continued and extended my 
researches this year, and indeed spent some little time on the coast of Brittany with 
this object, enjoying the hospitality of M. Lacaze-Duthier’s experimental laboratory 
at Boscoff. But my hopes were disappointed by the adverse weather which prevailed 
diming my stay there, and I succeeded in obtaining but few specimens. Neverthe- 
less I was enabled to place one fact beyond doubt — the existence, namely, of nerve- 
fibres in the velum of some at least of the Craspedota. On page 128 of their work, 
the Brothers Hertwig speak of having only by the most careful search been able 
to make out the existence in two genera ( Trachynema and Cunina) of tine fibrils, 
perhaps of nervous nature, taking a radial direction in the velum beneath the epi- 
thelium of the under side. In a specimen of Thaumantias (species ?) I observed in the 
living animal distinct nerve-fibres like those I had seen in the subumbrella of Aurelia. 
They passed outwards from the nervous ring, becoming gradually finer until lost near 
the free edge of the velum, and since they exhibited no nucleated enlargement I 
conclude with the Brothers Hertwig that they spring from ganglion-cells in the ring. 
October, 1878. 
* Das Nervensystem und die Sinnesorgane der Medusen. Monographisch dargestellt von Oscar 
Hertwig und Richard Hertwig. Mit 10 litkograpliirten Tafeln. Leipzig, 1878. 
f Claus (Studien iiber Polypen und Quellen der Adria. Denkscbriften der Wiener Akademie, 1877) 
seems to Lave noticed tbe peculiar character of the ectodermic cells in this fovea in Aurelia. He has 
advanced the hypothesis that it represents a rudimentary olfactory organ, and has given it a name in 
accordance with this hypothesis ; hut it would he difficult to put the opinion to experimental proof. The 
ganglion- cells in the suhumbrella of Cliryso.ora are also noticed by Claus, but His statement as to the 
existence of ganglion-cells under the nerve-epithelium I am unable to confirm. 
4 E 
MDCCCLXXVIII. 
