DRS. CARPENTER AND CLAPAREDE ON TOMOPTERIS ONISCIFORMIS. 61 



at a certain stage of development, are fringed with long cilia Ijotli at their margins and 

 at their base ; but the cilia are only occasionally to be seen in activity ; and we suppose 

 it to have been either from the absence of the cilia, or from their not having been in 

 motion, that they escaped the notice of Mr. Huxley, who describes the epaulettes as 

 rounded elevations on either side of the narrow neck, from which a sort of band or ridge 

 runs back upon the dorsal surface (vol. xxii. p. 359). No trace of these organs is to be 

 seen in the earlier stages of the animal's life. 



The lens-like body in each of the pair of ocelli (fig. 12. b, b) which are seated upon the 

 bilobed ganglion, is not single but double, as has been already stated by Leuckart and 

 Pagenstecher. 



We were able clearly to distinguish the spheroidal cells of which the biloljed ganglion 

 is composed ; and in its anterior part we noticed (as Leuckart and Pagenstecher had pre- 

 viously done) a pau' of vesicles imbedded in its substance (fig. 12. a, a). These vesicles are 

 nucleated; but we could not distinguish either otoliths or ciliary movement in their 

 interior. How far they are to be considered as analogous to the auditory vesicles of other 

 Invertebrata, we are therefore unable at present to determine. 



After a careful search for nerve-fibres in connexion with these ganglia, we feel unable 

 to speak positively either as to their presence or their absence. There is certainly some 

 appearance of a nerve-fibre on either side passing from the ganglion towards the frontal 

 part of the head (as described by Leuckart and Pagenstecher), and also of one passing 

 into the base of the second antennae (as noticed in the former memoir) ; but we are not 

 at all sure that these appearances are to be trusted, having now satisfied ourselves that 

 the linear trace which passes on the median line along the dorsal surface is not (as was 

 suggested in the former memoh' that it possibly might be) a band of fibrous nerve-sub- 

 stance, but is simply the mark of the attachment of a mesentery by which the intestine 

 is held in its place. We have been unable, notwithstanding our careful and repeated 

 search for it in living specimens, to detect the ventral nervous cord and oesophageal ring 

 described by Grube (see vol. xxii. p. 361) ; and we cannot but believe that he must have 

 been deceived by appearances prodiiced by the change which the textures of this deli- 

 cate creature had undergone in the process of conservation to which his specimens of it 

 had been subjected. 



The observation of a considerable number of specimens in various stages of develop- 

 ment enables us now to state that the alimentary canal may present itself at any period 

 either in the state of contraction shown in Plate LXII. fig. 1 (vol. xxii.), or in that of dis- 

 tention shown in Plate VII. fig. 6, or in any intermediate condition. Even when the canal 

 has been most distended, however, it has generally seemed to contain little else than water, 

 very few solid particles being visible in its interior. In one individual, however, we ob- 

 served in the intestine several fragments of a Beroe which had been captured at the same 

 time and had been broken in the tow-net ; and these fragments were kept in continual 

 agitation by the persistent movements of their large cilia. This unusual exercise of vora- 

 city seemed to have an injurious efi'ect upon the individual; for it was found dead th^ 

 next morning, whilst several other specimens in the same jar survived. The caudal pro- 

 longation of the body is generally in a state of greater or less contraction longitudinally ; 



