. Bulletin - United States National Museum. Science. vol. 2, pt. 2.] A TAXONOMIC STUDY OF THE SALPIDAE METCALF. 19 1899). In some other species they are clearly glandular, forming the secretion by proliferation of cells from the epithelium and their degeneration. In the Salpidae the neutral glands arise from the epithelium of the pharyngeo-atrial chamber, in a manner described by Metcalf (1892, 1893, b and c). This is entirely different from the neural gland of Ascidians and Pyrosoma, which arises from the wall of the neural tube. The gland in Ascidians and Pyrosoma opens into the dorsal tuber
. Bulletin - United States National Museum. Science. vol. 2, pt. 2.] A TAXONOMIC STUDY OF THE SALPIDAE METCALF. 19 1899). In some other species they are clearly glandular, forming the secretion by proliferation of cells from the epithelium and their degeneration. In the Salpidae the neutral glands arise from the epithelium of the pharyngeo-atrial chamber, in a manner described by Metcalf (1892, 1893, b and c). This is entirely different from the neural gland of Ascidians and Pyrosoma, which arises from the wall of the neural tube. The gland in Ascidians and Pyrosoma opens into the dorsal tubercle by a duct which is the persistent anterior end of the nerve tube. In the Salpidae the neural glands have never at any time any connection with the dorsal tubercle or the nerve tube, its ducts, like the glands themselves, coming from the epithelium of the pharyngeo- atrial cavity. There seems, at first thought, no ground for any homology between the neuralglands in Salpidae and the neural glands of other Tunicates, and we have no fully convincing reason for believing their functions to be the same. But com- mon function and true ho- mology between the glands of Salpa and the gland of Ascidians is suggested by the conditions in Ascidia mammittata and some of its nearest relatives, in which the very slender and greatly elongated duct leading from the neural gland to the ciliated funnel1 is much branched laterally, these branches connecting with the pharynx by small ciliated funnel-shaped pores. In these forms, the neural gland opens to the pharynx by the ciliated funnel proper and also by very numer- ous lateral In other Ascidians the neural gland opens only by way of the ciliated funnel. Embryonic Salpas and young buds have the neural tube opening forward into the ciliated funnel, but they have no neural gland. Later the neural tube closes and its connec- tion with the ciliated funnel is lost. Then a new type of neural gland, as described, developes from the pharyngeo
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