. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). 180 IN VERTEBRA TE MORPIIOLOO Y. rm also found in Maimmaiia and in exceptional cases in man. A great uniformity of structure exists throughout all the species, so that they are all referable to a single genus, Echinorhynckus.' The body (Fig. 90) is cylindrical and as a rule not very long, and a marked distinction from the Nematodes is found in the retractile proboscis {pr) occurring at the anterior end of the body. It is a cylindrical prolongation of the anterior portio
. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). 180 IN VERTEBRA TE MORPIIOLOO Y. rm also found in Maimmaiia and in exceptional cases in man. A great uniformity of structure exists throughout all the species, so that they are all referable to a single genus, Echinorhynckus.' The body (Fig. 90) is cylindrical and as a rule not very long, and a marked distinction from the Nematodes is found in the retractile proboscis {pr) occurring at the anterior end of the body. It is a cylindrical prolongation of the anterior portion of thebody and is provided with a number of chitiuous hooks by means of which it adheres to the intestinal wall of its host. The proboscis may be invagi- nated into a double-walled muscular proboscis-sheath by whose contraction it may again be protruded, a strong retractor muscle, extending from the tip of the proboscis to the base of the sheath, serving for the invagination ; and from the base of the sheath re- tractor muscles {rm) pass to the body- walls and serve to hold the sheath in position. No traces of a digestive tract occur. The body is covered upon the out- side by a thick cuticle secreted by the subjacent hypodermis, which is a rather Fig. 00.—Male Ecldnorhyn- thick laj'er consisting of a protoplasmic c/A«s (aft*..-lkuckaiit). matrix in which nuclei are scattered but in which no cell-outlines are to be distinguished. Beneath the cuticle the matrix has a fibrillar character, and near its inner surface it is hollowed out into a network of anastomosing canals of which mention will be made later. Beneath the hypodermis lies a basement-membrane within which are two layers of muscle-cells, having the same epi- thelio-muscular character as those of the Nematodes, the fibres of the external layer having a circular direction, while. g = glands. I = lemniscus p = penis, pg = proboscis ganglion pr = proboscis. rm = retractor muscle. I = Please note that these i
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
