. . the side of theAnnelidan prostomium or upper lip of the has already been pointed out that the bending ofthe head has changed its position from behind themouth to in front of it. The form of this limb needs no special comment ;the bend in it is not a true joint, nor is it providedwith any muscles except a few which run into the bulbon which it stands. Its setae are modified into sensoryhairs, homologous with the olfactory hairs of thehigher Crustacea. Morphologically, the first antenna must be regarded D 34 THE PART I
. . the side of theAnnelidan prostomium or upper lip of the has already been pointed out that the bending ofthe head has changed its position from behind themouth to in front of it. The form of this limb needs no special comment ;the bend in it is not a true joint, nor is it providedwith any muscles except a few which run into the bulbon which it stands. Its setae are modified into sensoryhairs, homologous with the olfactory hairs of thehigher Crustacea. Morphologically, the first antenna must be regarded D 34 THE PART I as the sensory cirrus of the parapodium of the firstsegment, the parapodium itself having disappeared, orpossibly being represented by the bulb on which theantenna stands ; this latter homology is, however, verydoubtful. Though the parapodium itself has dis-appeared, the gland of its aciculum is probably stillpresent, and functions as a salivary gland. Fig. 29p. 114, shows the position and form of this gland. Acomparison of this figure with Fig. I will make it. B FIG. 7.—A. First antenna (L Spitzbergensis) \v\ti\ hooked sensory hairs, homolo-gous with the olfactory hairs of the higher Crustacea, c, the sensoty cirrus ; d,the bulb on which it stands, perhaps the remains of the dorsal parapodium onwhich it stood. B. Second antenna (L. Spitzbergensis) showing the rudimentsof the endopodite, of the distal end of the dorsal parapodium which hadbeen highly developed in the Nauplius. but is degenerated in the adult; c, thesensory cirrus. clear that this gland can be so homologised ;—thepoint will, however, be discussed in detail in connec-tion with the description of the gland itself. FromFig. I it will be seen that the acicular gland of the(vanished) parapodium of the first segment couldeasily open within the mouth, on the under lip. SECT, in THE APPENDAGES 35 II. 77/t second pair of Antenna (Fig. 7 />)--Thcsecond antenna is so much reduced in the Apodidaethat its absence
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherlondo, bookyear1892
