Discovery reports (1962) Discovery reports discoveryreports30inst Year: 1962 4oo DISCOVERY REPORTS In Physalia two sorts of flagellum occur, and they are found in large numbers. They are best seen in gastrozooids fixed while feeding, the buccal endoderm being spread out as a flat sheet (PI. XXVII, fig. 7). They occur in rows. The shorter flagella (about 10 fi in length) occur in groups of about a dozen. The long flagella (about 25 /i in length) are more closely bunched together, and occur in groups of about half a dozen. These numbers are rather variable. The short flagella seem to arise fro
Discovery reports (1962) Discovery reports discoveryreports30inst Year: 1962 4oo DISCOVERY REPORTS In Physalia two sorts of flagellum occur, and they are found in large numbers. They are best seen in gastrozooids fixed while feeding, the buccal endoderm being spread out as a flat sheet (PI. XXVII, fig. 7). They occur in rows. The shorter flagella (about 10 fi in length) occur in groups of about a dozen. The long flagella (about 25 /i in length) are more closely bunched together, and occur in groups of about half a dozen. These numbers are rather variable. The short flagella seem to arise from the centre of the cells, the larger from the sides. Both sorts of flagellum can probably occur in one and the same cell, but this is not always the case, and groups of the longer sort are in a minority. The blepharoplast in both types is single, not double as in Hydra. The endoderm throughout Physalia is flagellated, but the bunches of long flagella are confined to the buccal cells of the gastrozooids. 1 mm Text-fig. 6. Transverse section through a gastrozooid in the basal region, ec = ectoderm, en = endoderm, mes = mesogloea, v = villi, cut at various angles. Turning now to the basal region of the gastrozooid, we find a more complicated organization of the endoderm. The most conspicuous features are the villi. These are finger-like projections from the lining of the zooid, consisting of endoderm cells covering a central core of mesogloea (Text-fig. 6; PI. XXVII, fig. 6); the ectoderm is not involved. The villi can be seen through the transparent wall of the zooid (Text-fig. 4). The endodermal cells of the villi are probably all of one type; they are quite clearly active in intra- cellular digestion. In certain specimens, which had been feeding shortly before fixation, the enteron is filled with a mixture of partly-digested flesh, pigment, both dispersed and in aggregates, and nematocysts, discharged and undischarged. The same objects have been identified in vacuoles in th
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