OR OSSEOUS SYSTEM. 25 



parasitic worms, which are found attached to the exterior 

 surface of the gills, the lips, the eyes, and other soft parts 

 of fishes, and which have thence been called epizoa. We 

 already find in many of these animals, as in the lerncea 

 and chondrocanthi, not only the head forming a distinct 

 segment of the body, and the trunk partially divided by 

 transverse depressions, but numerous appendices already 

 developed from the sides of these segments, and some of 

 these appendices, especially on the head, provided with move- 

 able articulation. This dense covering is still so transparent 

 and hermogenous, that we can distinctly perceive through it, 

 the longitudinal muscular fibres which produce the numerous 

 corrugations of the skin, and also the contained viscera. 

 The transition is quite imperceptible from these epizoa, as 

 the tracheliastes and the achtheres to the fixed parasitic 

 entomostracous crustaceous animals, as the ergasilus and the 

 lamproglena, where the exterior covering has the same 

 texture and properties, and where the articulated appearance 

 of the trunk and its appendices is nearly in the same simple 

 condition. One of these lowest of the entomoid tribes 

 almost inseparable from the epizoa, the lamproglena pulchella, 

 is represented in Fig, 10, B. where we already observe the 

 head and three principal divisions of the thorax distinctly 

 marked, as in insects. We perceive in this little animal, 

 found attached to the gills of the cyprinus jeses, two pairs of 

 maxillae, a, a, b, b, formed like curved pointed feet, and two 

 pairs of antennae c, c, d, d, as in higher Crustacea. Above the 

 mouth e, are seen the two eyes united on the median plain as 

 in higher monoculi, and the intestinal canal /*, is observed 

 surrounded by the follicles of the liver, and passing straight 

 through the middle of the whole body, as in most parasitic and 

 carniverous articulata. Pairs of feet, ^, q, r, are seen extending 

 from the sides of the segments, and transverse fasciculi of 

 muscular fibres i, h, k. The unimpregnated ovaries /, closed 

 above and filled with imperfectly developed ova which after- 

 wards descend to external sacs, open on each side of the 

 last distinct segment by a trilobate orifice m. All the ex- 

 ternal parts of this very minute animal are developed nearly 

 to the same extent, and articulated to as great a degree in 

 the achtheres and several of the higher of the acknowledged 

 epizoa ; so that we have already developed in the lowest of 



