SOLENOGASTEES. 5 



tissue and muscles. The course of these muscles is difficult to trace ; they surround 

 the radula-sac and the distal portion of the ventral pouch ; a very broad transverse 

 muscle takes its course between the radula-sac and the ventral pouch (Fig. 10, m). 

 Around the salivary glands a thin muscular layer likewise occurs. I do not know 

 how to explain the mechanism of the radular movement. No doubt, the diverse 

 muscles allow of movement in various directions. 



A subradular organ, as found by Heath (1) in Proneomenia and Rhopalomenia, 

 IS wantmg. 



The spacious intestine is formed by the coalescence of the already described 

 portion of the digestive tract with the dorsal caecum (Fig. 8). I have avoided making 

 use of the names pharynx and oesophagus, as there cannot be question here of any 

 sharp separation between the two, even though the proximal part is of a different 

 structure from the following portion. Thiele mentions a strong fold in which the 

 salivary glands open out, and which separates pharynx from oesophagus (13, p. 288). 

 A similar condition does not exist here. An oesophagus, in the sense Thiele ascribes to 

 it, fails entirely. 



The spacious intestine shows strongly folded walls, with the exception of the 

 dorsal wall, which remains smooth, except in the median line, where a small fold 

 occurs. The dorsal wall carries cilia ; the ventral and lateral walls show glandular 

 epithelium. Lateral caeca are met with as usual ; the transverse sections do not teach 

 much in regard to their relative situation. The rectum has strong cilia (Fig. 21, r). 



The cloaca with its strongly folded wall opens to the exterior through a wide 

 longitudinal slit. Gills are entirely wanting. The wall of the cloaca is very thick and 

 consists of several layers of small transparent cells with small nuclei, between which 

 slender ciliated supporting cells occur with narrow long nuclei, which stain well 

 (Fig. 19). As it seems to me, the wall of the cloaca does not perform any respiratory 

 function, it being too thick. A secretory function must not be excluded. Oftentimes 

 in the cloaca and against its wall little feebly staining globules are found, which I 

 believe to be formed by the wall-cells of the cloaca. Yet we must take into 

 consideration that the cloaca is surrounded by extremely loose connective tissue with 

 large spaces, filled with blood-corpuscles. This arrangement more especially obtains 

 in that part of the cloaca which is contiguous with the dorsal lip ; this part is entirely 

 surrounded by blood-corpuscles, and, as it is only clothed by a single layer of epithelial 

 cells, a respiratory function may be ascribed to it. The lateral walls of the ventral 

 slit, by which the cloaca communicates with the exterior, are coated with ciliated 

 cylindrical epithelial cells (Fig. 19). 



Properly speaking, the praecloacal organ does not open into the cloaca, but into 

 the ventral slit, as well as both cloacal spicules (Figs. 19, 20). The latter (Kloaken- 

 spicula of Thiele) are well developed, and consist of small bars of about • 75 mm.. length. 

 These bars are probably calcareous. Around the bars a strong envelope is found, 

 which is not dissolved in nitric acid, but stains easily with carmalum. Probably 



