. Outlines of zoology. ta. In the last there arefive pairs in the larva, and two persist. If there be arelationship between Enteropneusta and Annelids, it mustbe a very distant one, perhaps restricted to origin from somecommon stock. Class Pterobranchia. (i) Cephalodiscus Cephalodiscus dodecaiophm was dredged by the Challenger in theMagellan Straits. Others are known from Japan, the Malay Archi-pelago, South Africa, and the Antarctic. It was at first described byMIntosh as a divergent Polyzoon, but the researches of Harmer pointto relationship with Balanoglossus. PTEROBRANCHIA. 441 The minute
. Outlines of zoology. ta. In the last there arefive pairs in the larva, and two persist. If there be arelationship between Enteropneusta and Annelids, it mustbe a very distant one, perhaps restricted to origin from somecommon stock. Class Pterobranchia. (i) Cephalodiscus Cephalodiscus dodecaiophm was dredged by the Challenger in theMagellan Straits. Others are known from Japan, the Malay Archi-pelago, South Africa, and the Antarctic. It was at first described byMIntosh as a divergent Polyzoon, but the researches of Harmer pointto relationship with Balanoglossus. PTEROBRANCHIA. 441 The minute individuals are associatedtogethei! within a gelatinous investment;the colony may attain a size of 9 6 in. The gut is curved, the anusbeing beside the mouth, beneath whichare 4-6 pairs of arms with ciliated tent-acles. These two characters, formerlysupposed to indicate Polyzoan affinities,may perhaps be adaptations to the sedent-ary life. With Balanoglossus this type hasbeen compared, on account of the possession. Fig. 239.—An individual Cefhalo-discus.—After Ridewood. Buds; si., stolon; go., to the left,bulging of the body caused by thegonad ; ga., to the right, bulging of thebody caused by the stomach ; j*.j., pos-terior lobe of buccal shield ; , a redline on the buccal shield; , darkedge of the buccal shield; pi. tentacularplumes.
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
