. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). TYPE CRUSTACEA. 433 probably aerviug for swimming. The abdomen was com- posed of twelve segments, the anterior six of which were much more massive than the others and bore five pairs of platelike appendages on whoso posterior surface were the branchijB. The terminal segment bore a spine or tinlike structure. Such a form as this, represented by the genus iLhirypterus (Fig. 198), presents strong similarities to Limulus and also to the Scorpions, bearing out the numerous
. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). TYPE CRUSTACEA. 433 probably aerviug for swimming. The abdomen was com- posed of twelve segments, the anterior six of which were much more massive than the others and bore five pairs of platelike appendages on whoso posterior surface were the branchijB. The terminal segment bore a spine or tinlike structure. Such a form as this, represented by the genus iLhirypterus (Fig. 198), presents strong similarities to Limulus and also to the Scorpions, bearing out the numerous similarities of structure occurring between Limidm and those forms. This side of the affinity may be postponed, however, until the next chapter, and the comparison of Limidus with the Crustacea discussed here. Its chitiuous cuticle, its jointed and biramous appendages, and its branchial respiration show similari- ties to the Crustacea, as do also the form of the heart and the compound eyes. Whether or not the coxal gland is comparable to the shell- gland is at present uncertain, but the other similarities are sufficient to justify the recognition of a Crusta- cean origin for Limvlus. It iov\x\H Y\Q.\9Q--Eurypteru8remipe8 indeed a connecting link between the (from Nicholson). Crustacea and t.'ie Arachnida, presenting probably on the whole more affinities with this latter group than with the former. Since, however, a Crustacean ancestry is probable, a com- parision of the appendages of Limulus with those of a repre- sentative of the ancestral group ouguu *o be possible. It has already been noticed that the brain of Limulus is a syncere- brum composed of three segments; it represents, therefore, two segments of which the appendages and other parts have disappeared. Furthermore, recalling that, in the higher Crustacea at leafjtj a ganglion occurring between the cerebral antennary ganglia in the embryo indicates a lost pair of. â :.i' *â ;. Please note that these images are e
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
