356 DR. W. B. CARPENTER ON TOMOPTERIS ONISCIFORMIS. 
ing to the styliform appendage; and the membranous sheath of its stylet was studded at 
intervals with isolated red granules or minute cells, which appeared to me to be connected 
by delicate fibres having the same general resemblance to the axis-band of ordinary nerve- 
fibres. I do not speak with any confidence on this point; more especially on account of 
the å priori improbability of the longitudinal nerve-cord being on the dorsal aspect of the 
body. But I think it right to record the fact of the constant presence of these red spots 
(of which very little notice has been previously taken), and of the apparent existence of 
fibres passing between them. 
The impression at first left on my mind by the study of this interesting creature, of 
which I had never before seen or heard any account, was that it was a larval form, per- 
haps of an Annelid, but not impossibly of some Isopod Crustacean ; the latter notion . 
being suggested by its strong resemblance in habit to the Branchiopod forms of that 
class. I tried every expedient I could think of, for preserving specimens for subsequent 
examination and exhibition; but I could not succeed. Any medium in the slightest 
degree different in density from sea-water caused either an immediate endosmose, by 
which the body was made to burst, generally at the ends of the members; or an exosmose, 
by which it was at once shrivelled-up; and the tendency to disintegration which I have 
already noticed as showing itself even during life, operated still more strongly so soon as 
life became extinct. vo 
Not many days after I had made the observations already detailed, I captured a speci- 
men of larger size, having twelve pairs of fin-like appendages, and a caudal prolongation. 
destitute of appendages,—its structure being in every other respect the same. And after _ 
a few days more I was fortunate enough to obtain (along with several specimens of the 
younger form) the specimen represented in fig. 6, which can scarcely be considered as 
anything else than another phase of the same type. Its entire length was about 24 times 
as great; but of this only about the anterior three-fifths corresponded in structure to the 
original, the posterior two-fifths being obviously an addition formed upon a very different 
plan. Looking first to the anterior portion, we observe that it differs from fig. 1 in the 
following particulars. The head appears to carry on its front only one pair of horn-like 
appendages; a careful examination, however, shows that the second or smaller pair is 
really present, though, from its arising from the under side of the peduncle (which is 
here relatively shorter), it is concealed by the anterior part of the head when viewed from 
the dorsal aspect. The styliform appendages are greatly increased in relative length, soas _ 
even to pass considerably beyond the anterior three-fifths of the body. | | 
The number of fin-bearing ppendages is now siæteen; of these the first eight are nearly 
of equal size; and there is then a gradual diminution down to the 16th, which, though 
comparatively small, present 
+ Presents the structure characteristic of the rest. The alimentary 
canal, instead of being limited to a portion of the cavity of the body, now fills it entirely, 
except in the pharyngeal region; and it' seems to be in a state of constant distension, 
except where narrowed at 
ally passes from the mouth to the anus. 
13th pairs of fin-like appendages, and is s 
structure of the canal remains quite 
Such a narrowing is seen between the 12th and 
hown on a larger scale at the top of fig. 7. The 
simple as far as the 16th pair of appendages, and 
any part by a wave of peristaltic contraction which occasion 
