Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 433 343), the larva still resembles a Nauplius, and it is only after another moult that it is transformed into the first Ci/cIops-\ike form. It then resembles the adult animal in the structure of the antennte and mouth parts, although the number of the appendages and the body rings is smaller (tig. 342, c). The two last pairs of appendages already have the form of short biramous swimming feet, and the rudiments of the third and fouth pa
Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 433 343), the larva still resembles a Nauplius, and it is only after another moult that it is transformed into the first Ci/cIops-\ike form. It then resembles the adult animal in the structure of the antennte and mouth parts, although the number of the appendages and the body rings is smaller (tig. 342, c). The two last pairs of appendages already have the form of short biramous swimming feet, and the rudiments of the third and fouth pairs of swimming feet have made their appearance as projections beset mth set*. The body consists in this stage of the oval cephalothorax; the second, third and fourth thoracic segments; and an elongated terminal portion, which gives rise to the last thoracic segment, and to all the abdominal segments by a pro- gressive segmentation, and already terminates in the caudal fork. Fio. 3^.—Actheres percarum.—a, Nauplius form, h, Lar\'a in the youngest Cyclops stage; Kf, Kf', maxillipeds. c. Female seen from the ventral side. Ov, Ovaries ; KD, cement glands, i. The smaller male seen from the side ; Mxf, Mxf', maxillipeds. Many forms of parasitic Copepoda, for example Lernanthropus and Chondracanihus, do not get beyond this stage of body segmenta- tion, and obtain neither the swimming feet of the third and fourth pairs, nor a fifth thoracic segment separate from the stump-like abdomen; others, for example Achtheres, by the loss of the two anterior pairs of swimming feet, sink back to a still lower stage (fig. 344). All the non-parasitic and many of the parasitic Copiepioda pass in the successive moults through a larger or smaller number of de- velopmental stages, in which the still undeveloped segments and appendages make their appearance, and the appendages already 28
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