ACAiEPIITE. 1 7 



colour, in Cydippe and Eiicliaris, of a reddish tinge in Beroe. These 

 corpuscles vibrate by the action of the cilia of the lining epithelium 

 of the cysticle. Some superimposed dark-coloured pigment-cells 

 render its situation conspicuous. By some anatomists the combined 

 cysticle and pigment-cells have been regarded as a simple organ of 

 vision, by others as a simple organ of hearing ; both would probably 

 be right if they would limit the one sense to the pigment spot, the 

 other to the cysticle. The remarks by M. Agassiz on the nervous 

 system of the Beroidse appear to me so just, and accord so well with 

 the conclusions to which my ow^n observations have led, that I cannot 

 better conclude my notice of this part of the ciliograde structure than 

 by quoting them : — 



" As for the nerves which are said to arise from the ganglion con- 

 nected with this black speck, I have been unable to make them out. 

 I have seen numerous muscular or contractile fibres connected with 

 the lower extremity of the chymiferous 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 con- 

 tractile fibres have ; again, I have repeatedly seen these fibres in a 

 state of contraction or relaxation, presenting 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 Medusfe. I am even satisfied, fi'om 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 by some ; and when Professor Grant states that Beroii has 

 eight nervous threads, I suppose he alludes to the eight narrow 

 chymiferous 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" (the cysticle), "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 Medusas. 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 pi'ecision and distinctness with 

 which it is mentioned. And I express these doubts notwithstanding 

 the doubts I have myself respecting the real nature of some organs 

 around the central black speck, for the very reason that, after findin"- 

 there more than has been seen and described, and various things 



