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DR. W. B. CARPENTER ON TOMOPTERIS ONISCIFORMIS. 356 



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 Brancluopod 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 sliifting 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 styltform appendages 

 and the first pan- 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 chrect 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 sho\\"n in figs. 3, 5. No 

 indications whatever of a dorsal vessel could be distingmshed ; but the flmd which occupied 

 the large perivisceral space of the body, head, and appendages, could be seen to contain 

 within it minute semipeUucid 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 respu-ation, and I did not observe ciliary motion on 

 any part of the surface. For the reasons already mentioned, however, I would not take 

 upon myself to affirm its non-existence. 



In the head there could be plainly distinguished a bilobed mass haAdng 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. Erom the central portion of the ganglionic 

 mass, I thought that I could distinguish something very like the axis-band of a 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 di^-isions of the body. 

 From each side of the bilobed ganglion I thought that I coixld trace a similar fibre pass- 



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