. Text-book of embryology. Embryology. VIII AETHEOPODA 215 ming appendages. In subsequent moults a varying number, but in no case do all the remaining segments of the thorax develop swimming appendages. Thus in Crangon only one extra segment develops forked appendages (Fig. 162), in Cheraphilus two segments develop. Fig. 162.—"Mysis" larva of Crangon AUmanni, lateral view. (After Sars.) tel, telson ; exp^'S the four exopodites borne by the three maxillipedes and great chela respectively ; pJE, pleopods (abdominal appendages); w/-, uropods (last abdominal appendage); tli^'^^ the appen
. Text-book of embryology. Embryology. VIII AETHEOPODA 215 ming appendages. In subsequent moults a varying number, but in no case do all the remaining segments of the thorax develop swimming appendages. Thus in Crangon only one extra segment develops forked appendages (Fig. 162), in Cheraphilus two segments develop. Fig. 162.—"Mysis" larva of Crangon AUmanni, lateral view. (After Sars.) tel, telson ; exp^'S the four exopodites borne by the three maxillipedes and great chela respectively ; pJE, pleopods (abdominal appendages); w/-, uropods (last abdominal appendage); tli^'^^ the appendages _ whicli will form the five pairs of wall^ing legs. appendages with exopodites, in Pontophilus two, and in Sabinea one only. Those segments that do not develop swimming appendages give rise to simple, unforked appendages, which at the last moult develop directly into the hinder walking legs of the adult, as in the case of the Loricata, and we may add, as in the case of the Mysis larva which develops out of the Zoaea larva of Thalassinidae, another family of the Caridea. Finally, in the Brachyura all the thoracic segments behind the first two which bear the swimming appendages of the Zoaea, develop only rudimentary bud-hke appendages whilst the larval swimming stage persists, but when this is over and the larva begins life at the bottom, then these appendages develop directly into the walking legs without ever passing through a forked stage. Thus, in the life-history of the crabs the Mysis stage has been completely eliminated, but nevertheless the Zoaea does not change into the adult stage but into a form called a Megalopa, in which the carapace is longer than broad, and in which all the seg- ments of the abdomen possess well-developed swimming appendages. This larva obviously represents a Macruran stage in the ancestry of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearanc
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