DR. W. B. CARPENTER ON TOMOPTERIS ONISCIFORMIS. 861 
. of the body are bifid, and in large specimens the lobes of the posterior not-fully-developed 
appendages are relatively larger than the former. One of the most important parts 
of Grube's memoir relates to the nervous system. He asserts that he has distinctly seen, 
in many specimens, a double nervous cord passing backwards along the ventral surface of 
the body from an cesophageal ring, of which the upper part is formed by the cephalic 
ganglia. This double cord, he says, does not anywhere present ganglionic enlargements ; 
but, when examined under a high magnifying power, it presents a series of transverse 
striæ at short intervals. I cannot but express some doubt as to the existence of this 
ventral cord; for Grube’s description of it is entirely based upon preserved specimens * ; 
and although I looked for it carefully and repeatedly in living specimens, I was not able 
to detect it. Grube's description of the muscular structure also, especially in the fins, is 
very minute; but I can state confidently that this presents itself under a very different 
aspect during life; indeed, as to the general histology of the creature, I was struck with 
the remarkable change which it seemed to undergo when the animal appeared to be 
suffering from confinement, but while as yet far from having lost its vital activity. 
The most recent notice of Tomopteris is that given of it by Mr. Gosse in his * Natu- 
_ralist’s Rambles on the Devonshire Coast’ (p.356), under the name of Johnstonella 
Catharina; it adds nothing, however, to what had been previously recorded, excepting as 
to the occasional eversion of the pharynx so as to form a protruded proboscis, which 
Mr. Gosse seems to have been the first to observe. His specimens appear to have been 
in the same stage of development as my most advanced specimen, having 16 pairs of 
fin-like appendages, and a caudal prolongation without any obvious appendage. He - 
seems to have overlooked the posterior pair of frontal * horns," which, for the reason I 
have stated, are not to be seen in the larger specimens unless carefully looked for. In 
his ‘Marine Zoology ” (vol. i. p. 106), Mr. Gosse has introduced Tomopteris (by its proper 
designation) amongst the * animals of doubtful position, probably belonging to the Anne- 
lida ;” and he has given a figure of it, which, like the figure in his * Devonshire Coast, 
wants the second pair of frontal * horns," and which is further erroneous as giving not 
_ the least indication of the bifid character of the fin-like appendages. 
There cannot, I think, be any longer a reasonable doubt as to the Annelidan character 
of Tomopteris; and the principal point which now requires investigation seems to me to 
be the question of the real nature of the caudal prolongation, —that is, whether it is 
simply an extension of the body, or is a zooid destined to be cast off and to maintain an 
independent existence. The former view seems to be that of all previous observers ; no 
such marked peculiarity having been observed by them, either in the conformation of its 
appendages, or in the structure of its integument and of the portion of the alimentary 
canal included in it, as that which seemed to me to differentiate it completely from the 
anterior part of the body, and to bring it nearer to the ordinary Annelidan type. I speak 
With diffidence, however, on these points, since I find myself at issue In regard to them 
* It would be interesting to know in what fluid these specimens were mounted ; as I tried all the ordinary media 
without succeeding in preserving in any specimens an approach to their life-like appearance. : 
VOL. XXII. B 
