. The Danish Ingolf-expedition. Marine animals -- Arctic regions; Scientific expeditions; Arctic regions. ACI'INIARIA 23 part of tlie body-wall in Edwardsia therefore differ in appearance from those of Isoedwardsia. In Edwardsia we find in this region a thick ectoderm without cuticle (textfigs. 6, 62) and with scattered nematocysts; in Isoedwardsia commonly, (but not always) a thin ectoderm, always provided with cuticle, and the nemato- cysts enclosed in the nemathybomes (textfig. 69, compare below), The physa of the genus Edwardsia is probably always perforated by apertures. It is true that I
. The Danish Ingolf-expedition. Marine animals -- Arctic regions; Scientific expeditions; Arctic regions. ACI'INIARIA 23 part of tlie body-wall in Edwardsia therefore differ in appearance from those of Isoedwardsia. In Edwardsia we find in this region a thick ectoderm without cuticle (textfigs. 6, 62) and with scattered nematocysts; in Isoedwardsia commonly, (but not always) a thin ectoderm, always provided with cuticle, and the nemato- cysts enclosed in the nemathybomes (textfig. 69, compare below), The physa of the genus Edwardsia is probably always perforated by apertures. It is true that I have not examined all the specimens of Edwardsia, described here, in that respect, but as I have observed apertures in the physa of all the species {E. andresi, vegae, arctica, finmarchica, vitrca, longicornis), the aboral end of which I have thorouglily examined, it may not be precipitate to attribute such apertures to all Edwardsia-s])QCKS. To judge from the structure of the wall. â ^ Fig. 6. Fig. 7. Fig. 8. Textfig. 6. Longitudinal section of the proximal part of the body of Edwardsia andresi ne: nemathybomes, me: mesentery. The ectoderm of the physa is partly lost. â Textfig. 7. Transverse section of the upper part of the actinopharynx with parts of the mesenteries of Edwardsia daparedii. â Textfig. 8. A similar section in the lower part, si: siphonoglyphc. of the apertures of E. vegac it seems as if the apertures are invaginations of the ectoderm. The apertures are surrounded by a circular thickening, possibly of the ectoderm and forming a movable stopping wliich is directed outwards (textfigs. 50, 51) or inwards (textfig. 62), according to the different state of contraction of the physa. The endodermal muscles form a circular sphincter round the apertures. The other Edwardsiidae are probably devoid of aperture in tlie proximal end; I will, however, remark that I have not examined the proximal part of the column as thorouglily as in the genus Edimrdsia. The scapus is p
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Keywords: ., bookcentury1800, bookdecade1890, booksu, booksubjectarcticregions
