. Amphioxus and the ancestry of the vertebrates. Amphioxus; Sea squirts; Hemichordata. IXTEKXAL AXATOMY. 57 The individual groups of cells have an elongated and more or less ovoid shape with the long axis parallel to the long axis of the bodv. According to Langerhans their surface is ciliated. Two kinds of cells enter into their composition ; namely, large clear dilated cells, which are separated from one another by fine fibre-like cells of extreme tenuity (Fig. 2j). In the latter the nucleus of each cell is placed near the free end of the cell, while in the former it lies nearer the base of t
. Amphioxus and the ancestry of the vertebrates. Amphioxus; Sea squirts; Hemichordata. IXTEKXAL AXATOMY. 57 The individual groups of cells have an elongated and more or less ovoid shape with the long axis parallel to the long axis of the bodv. According to Langerhans their surface is ciliated. Two kinds of cells enter into their composition ; namely, large clear dilated cells, which are separated from one another by fine fibre-like cells of extreme tenuity (Fig. 2j). In the latter the nucleus of each cell is placed near the free end of the cell, while in the former it lies nearer the base of the cell. Langerhans found highh' refringent con- cretions in the dilated cells which he took for excretorv products. That these cells have a capacity for excreting waste matters has more re- centlv been shown experiment- ally by F. E. Weiss. The atrial epithelium on the pharyngeal papilla; ihe large cells contain con- barS has a similar character cretions indicated bv the black Fig. 27. — Isolated cells from renal ipilla; tl: etions ini (After L.\NGERH.\NS.) to that forming these curious renal papilla; on the floor of the atrium. The distribution of these papilla; in the vicinity of the atriopore is very irregular and variable and without any regard to a s\'m- metrical disposition. Although they are undoubtedly to be regarded as a species of renal organ, yet they could not be compared to any portion of the excretory system of the higher \*ertebrates. Another structure, or pair of structures, which has been considered to belong to the category of renal organs must next be referred to. This consists of two funnel-shaped diverticula of the atrial cavity lying in the dorsal (subchordal) ccelom in the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Willey, Arthur, 1867-. New York, London, Macmillan
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