. Text book of zoology. Zoology. Sub-Glass 2. Malacostraca. Ordelr 6. Becapoda. 225 exopods. Of the abdominal limbs tbe last pair, bowever, is not yet present. It is evident from this tbat the Cray-fish does not pass tbi-ougb a mysis-stage, nor, so far as is known, through a prawn-stage. The young ones cling for a time to the abdominal limbs of the parent. 3. The Oraw-fish {Palinurus) are large, spiny Crustaceans, which resemble Lobsters in most respects, although they difBer in that none of the ambulatory limbs (aU of which are of about equal strength) are modified as chelae; the second anten
. Text book of zoology. Zoology. Sub-Glass 2. Malacostraca. Ordelr 6. Becapoda. 225 exopods. Of the abdominal limbs tbe last pair, bowever, is not yet present. It is evident from this tbat the Cray-fish does not pass tbi-ougb a mysis-stage, nor, so far as is known, through a prawn-stage. The young ones cling for a time to the abdominal limbs of the parent. 3. The Oraw-fish {Palinurus) are large, spiny Crustaceans, which resemble Lobsters in most respects, although they difBer in that none of the ambulatory limbs (aU of which are of about equal strength) are modified as chelae; the second antenna is provided with a very long and strong fiageUum. A species living on English coasts, P. vulgaris, can produce a creaking sound by. Fig. 187. Phylloeoma, slightly enlarged. The four best developed pairs of i are : third maxilliped, first to third ambulatory legs. rubbing the peduncle of the second antenna against a median projection of the head. Scyllanis is nearly-related to the Craw-fish, btit differs from it in that the long multiartioulate feeler is replaced by a short, broad, unsegmented plate. The larva in both genera is very singular, hatching in the mysis-stage, although the hinder thoracic feet are not yet present; it is called Phyllosoma, and is chiefiy characterised by its leaf-like and flattened form; the carapace, through which the branching of the liver may be seen, is a flat plate, and does not cover over the whole thorax; the latter is a roundish disc, at whose edge the long locomotor limbs (the third maxillipeds and the ambulatory legs with small swimming-rami) are articulated. The abdomen is an unimportant appendage. 4. The Hermit-crabs (Pagurus) are characterised by having the abdomen modified into a large membranous sac with hardly any muscles, but almost entirely occtipied by the large liver, and the gonads, which have moved down from the thorax. The abdomen is concealed in an empty gastropod shell which the animal carries about; it is always asymmetrica
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
