The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . , there isreason to regard as the homologueof the hypophysis cerebri of thevertebrate brain. Julin and E. vanBencdcn have suggested that thefunction of this organ may possiblybe renal. The subneural gland, whichwas first noticed by Hancock, com-municates anteriorly, as UssofF (23)pointed out, by means of a narrowduct with the front of the branchialsac (pharynx). The opening of theduct is enlarged to form a funnel-shaped cavity, which may be foldedupon itself, convoluted, or evenbroken up into a nu
The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . , there isreason to regard as the homologueof the hypophysis cerebri of thevertebrate brain. Julin and E. vanBencdcn have suggested that thefunction of this organ may possiblybe renal. The subneural gland, whichwas first noticed by Hancock, com-municates anteriorly, as UssofF (23)pointed out, by means of a narrowduct with the front of the branchialsac (pharynx). The opening of theduct is enlarged to form a funnel-shaped cavity, which may be foldedupon itself, convoluted, or evenbroken up into a number of smalleropenings, so as to formcomplicated projec-tion, called the dorsaltubercle, situated in the dorsal part-, .of the prebranchia! zone. (fig. g). _ Fig. 9.—Diagrammatic sec- The dorsal tubercle in A menltila istion through anterior dorsal somewhat horseshoe-shaped (figpart of A. menlula. showmg 10); it varies in form in most Asci-the relations of the nene dians according to the genus andganglion, subneural gland, &c. species, and in some cases in the. DorsatTubercle. , Myelon. PP, Peripharyngeal , Subneural , Its duct. /, Test lining branchialsiphon. NervousSysletn. individual also. The function of th_neural gland must still be regardedas doubtful. The secretion is formedby the degeneration and disintegra-tion of cells proliferated from thewalls of the duct or its branches,and no concretions are found. Theciliated funnel of the dorsal tubercleIS a sense-6rgan, innervated by a large nerve from the ganglion;it may be a sense-organ for testing the quality of the water enteringthe branchial sac. The single elongated ganglion in the median dorsal line of themantle between the brajnchul and atrial siphons is the only nerve-centre in A. nunlula and most other Tunicata. It is thedegenerate remains of the anterior part of the cerebro-spinal nervous system of the tailed larval Ascidian (seebelow). The posterior or spinal part has entirely disappe
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
