2 H. F. NIEKSTRASZ. 



muscular layer by nervous threadss. I am also inclined to ascribe to the epidermal 

 papillae, and more especially to the granular cells amongst tlic transparent ones, a 

 secretory function, if not an excretory function as well. The purpose of such a 

 secretion is doubtful. Perhaps it prevents the cuticle from damage by causing small 

 particles to adhere to its surfoce. In any case, it is remarkable that the cuticle of tlie 

 Solenogastres is nearly always covered with a thin layer of mud firmly sticking to it. 



The spicules are formed in small cellular accumulations in the epidermis. Such 

 accumulations frequently occur, and consist of a few transparent cells (Fig. 3, A). In 

 one of the cells the .spicule is formed. This cell often has two nuclei, a fact which may 

 o-ive rise to the supposition tliat there are two cells that form the spicule. The 

 .spicules are pushed to the periphery of the cuticle, and are connected with the 

 epidermis by short stalks. The older spicules lose their connection with these stalks, 

 but preserve the mother-cells, which surround their base like a cap (Fig. 3, B). In 

 the case of the oldest spicules, however, this cap has also disappeared. Nowhere did 

 I meet with a formation of the .spicules such as Thiele described in Amphunenia 

 mapoUtana, Thiele (13, p. 246). Thiele is also of the opinion that it is one cell only 

 that produces a spicule. 



The ventral groove is distinct and deep. In it three folds of the epidermis are 

 found, a large and broad median fold and two small lateral ones. All three run as far 

 as the opening of the cloaca. Close before the latter the groove and the median fold 

 broaden considerably. The folds are formed of a single layer of epithelial cells. All 

 along the median fold the ventral glands open between its cells. These glands (" hintere 

 Baucihdriise," of Wiren) are strongly developed, especially at the proximal end of the 

 body, wliere they entirely surround the digestive tract (Figs. G-11, vg). They are 

 conspicuous by their more or less distinct vesicular structure and granular contents, 

 which stain intensely. At the proximal part of the body, amongst the strongly 

 developed ventral glands, voluminous anterior glands (" vordere Bauchdriise," of 

 Wire'n) are also found. They are of a more delicate structure, and stain much less 

 intensely (Fig. 6, ay). They open out between the epithelial cells which invest 

 the ciliated cavity (" Flimmerhohle," Fig. 0, '/). The latter is large, and divided by 

 a median dorsal fold. The wall carries strong cilia. 



There are two dorso-termiual sense organs situated on the distal lip behind the 

 cloaca. Fig. 5 shows three sections through the more proximal of these organs. The 

 epithelium (cjt*) shows an evagination (Fig. 5, C) into which the muscular layers and the 

 connective tissue continue (»<). This evagination separates ventrally from the epidermis 

 and pierces the thick cuticle {cut. Fig. 5, B). It forms a pedicle {peel.), upon which a 

 round kno]> is resting, the sense organ visible, at the surface of the cuticle (Fig. 5, A, 

 (Ito). The external layer of this knob consists of high epithelial cells, amongst which 

 slender, fine, easily staining cells are found, which I believe to be sense-organs. 



The mouth-slit is terminal and vertical. It leads into a spacious mouth-cavity, 

 provided with numerous ramified cirri, as is the case in other forms. A horseshoe- 



