DR. W. B. CARPENTER ON TOMOPTERIS ONISCIFORMIS. 355 
and by their incessant action the animal kept up a rapid swimming movement, varying 
continually in its direction, and very much resembling that of the Branchiopod Ento- 
mostraca, the strokes of the several appendages succeeding each other from before 
backwards. | | | 
Owing to the glass-like pellucidity of. this interesting little creature, its interior struc- 
ture can be made out as well as its continual restlessness allows; a further allowance 
having to be made for the circumstance, that owing to the difficulty occasioned by this 
very transparency in judging as to what is near and what remote, whilst its restlessness 
necessitates a continual shifting of the focal adjustment, the relative position of its in- 
ternal parts cannot always be determined without some liability to error. 
The mouth ordinarily opens by an elongated slit (fig. 3) on the underside of the head, 
into a thick-walled and apparently muscular pharyngeal cavity. This is shown in fig. 3 to 
be connected with the wall of the body by two bands on either side, one passing anteriorly 
- and the other posteriorly ; and it can scarcely be doubted that these are muscles for its 
protrusion and retraction, since I occasionally saw the pharynx protruded as a proboscis, 
after the fashion of many Annelids. About half-way between the styliform appendages 
and the first pair of fin-bearing appendages, the pharynx terminated by a well-marked 
constriction in the intestinal tube, which was a straight and simple canal whose diameter 
was usually no more than about a quarter of that of the body itself, and passed direct to 
the posterior extremity of the body, where it terminated with a pouch-like dilatation in 
the anal orifice (fig. 5). I never saw any solid matter in this canal; but it was frequently : 
distended in parts by water, a wave of which would occasionally pass peristaltically from 
one extremity to the other. When thus distended, its wall could plainly be seen to be 
chiefly composed of ovoidal cells very compactly arranged, as shown in figs. 8,5. No 
indications whatever of a dorsal vessel could be distinguished ; but the fluid which occupied 
the large perivisceral space of the body, head, and appendages, could be seen to contain 
within it minute semipellucid granules of irregular form and size, by whose movements it 
was made obvious that this fluid was continually shifting its place,—rather in conse- 
quence, however (as it appeared to me), of the general movements of the body, than of any 
more special provision for its circulation. . 
I could not detect any organs of respiration, 
any part of the surface. For the reasons already 
upon myself to affirm its non-existence. | | 
In the head there could be plainly distinguished a bilobed mass having all the appear- 
ance of a nervous ganglion; and upon this lay two little masses of pigmentary matter ‘ 
each of which bore a small pellucid lens-like body (fig. 2). There can scarcely, I think, 
be a reasonable doubt of these being ocelli. From the central portion of the ganglionic 
mass, I thought that I could distinguish something very like the axis-band ofa nerve-fibre 
without its tubular sheath, passing backwards along the dorsal surface of the body, keep- 
ing near to the median line, but not exactly upon it, and passing at intervals not very 
regular through red spots, which seemed like aggregations of granules, or very minute 
cells, and of which there were commonly six or seven in each of the divisions of the body. 
From each side of the bilobed ganglion I thought that I could trace a 
and I did not observe ciliary motion on 
mentioned, however, I would not take 
similar fibre pass- 
3A2' 
