﻿348 CONTRIBUTIONS TO THE NATURAL HISTORY 



are probably vascular dilatations of this ring, similar, in respect to the position where 

 they occur, to the bulbs of the funnel and the two threads between them extending 

 forwards and backwards are probably only outlines of the folds which form the cir- 

 cumscribed area. But there is no part of the structure of Pleurobrachia upon which I 

 can be less positive than upon this point. 



As for nerves which are said to arise from the ganglion connected with this black 

 speck, I have been unable to make them out. I have seen numerous muscular or 

 contractile fibres connected witli the lower extremity of the chvmiferous funnel ; I 

 have seen these fibres diverging from above the so-called ganglion, but have never 

 been able to trace any one of them beyond the length which contractile fibres have : 

 again, I have repeatedly seen these fibres in a state of contraction or relaxation, pre- 

 senting so little regularity in their distribution, that for the present I think it were rather 

 assuming to decide upon the disposition of the nervous system of Beroid Medusae. I 

 am even satisfied, from the descriptions published, that the eight converging narrow 

 tubes, of which I find no mention in former authors, must have been probably mistaken 

 for nervous threads bv some ; and when Professor Grant states that Beroe has eight ner- 

 vous threads arising from a central ganglion, I suppose he alludes to the central black 

 speck and its swollen base, and the eight narrow chvmiferous tubes, the connection of 

 which with the ambulacral tubes is so easily traced, though their central connection with 

 the vertical funnel still remains doubtful. I do not, however, deny that this centre is a 

 point where we have to look for at least one part of the nervous system, and the gelatinous 

 lobes about the mouth for the other part, if there be really a distinct nervous system in 

 Beroid, as in Discoid Medusae. But, for my own part, I have failed in tracing it out ; 

 though I may add, that I am sufficiently acquainted with the structure of the region where 

 it is said to have been observed, to doubt the accuracy of the statements which have been 

 made about it, especially in the precision and distinctness with which it is mentioned. And 

 I express these doubts, notwithstanding the doubts I have myself respecting the real na- 

 ture of some organs around the central black speck, for the very reason that, after finding 

 there more than has been seen and described, and various things which may answer 

 the vague descriptions given, I do not in reality find what has been said to exist in that 

 part of the animal. The points to which future investigations should be directed with 

 particular care are especially the relation which the central black speck may have with 

 the formation of Beroe as buds from Hydroid Polypi ; next, the connection of the eight 

 narrow tubes with the central funnel ; and finally, a more thorough investigation of the 

 tissues above the black speck and within the circumscribed area, and the apparent 

 termination of the narrow tubes. 



