ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 435 



in hardened sections polygonal spaces are to be seen which are 

 separated from one another by collecting canals, into which open a 

 number of cseca. In fact, the organ is a tubular gland, not unlike 

 that of the crayfish ; the tubes formed by a structureless memhrana 

 propria are filled with special polyhedral cells, varying in size and 

 frequently containing a number of fat-granules. The investing 

 envelope is resistent and formed of connective tissue. The author 

 proposes to investigate how far this organ has the function of a 

 pancreas, which it resembles in structure. 



Accessory Generative Organs of Terrestrial MoUnsca.*— Dr. A. 



Batelli's observations were carried on chiefiy upon Helix pomatia. 

 He confines himself as a rule to stating the bare facts. 



A common membrane covers all the sexual organs and is termed 

 serous ; it consists of an outer connective tissue, and of an inner 

 cellular formative layer, whose inner cells are irregularly aggregated, 

 forming a tissue resembling the connective membrane of KoUmann ; 

 the layer is structureless and fenestrated. The cells of the connec- 

 tive-tissue layer are globose and devoid of cell-wall, those of the 

 inner surface contain a dense non-vacuolated protoplasm ; the exterior 

 ones originate the connective fibres. The nerves are provided with 

 connective-tissue sheaths, their main trunks in the serous membrane 

 are flat and fibrillated and contain nerve-cells either singly or in 

 ganglionic masses at certain points. Three kinds of nerve-branches 

 are distinguished, viz. 1. Terminal, produced by the breaking up of a 

 large trunk into two or three of smaller diameter ; 2, Intermediate, 

 given off by the main trunk, without causing diminution of its dia- 

 meter — the neurilemma is continued uninterruptedly on to the 

 branches ; 3. Derived from cells. It is probable that elementary 

 fibres enter these peripheral nerve-cells of the serous membrane, 

 break up within them, and reunite at the further extremity into a 

 fibre : the neurilemma of the cell is continued over the fibre derived 

 from it. 



Of the different organs, the wall of the dart-sac is composed of 

 muscular fibres which lie chiefly on the external aspect, and of a 

 narrow connective-tissue layer which lies chiefly to the inner side of 

 the former, and is almost constant in thickness throughout the organ ; 

 the basal bulb is, however, chiefly muscular. Besides these, the sac is 

 lined by an epithelium of long cylindrical cells, elongated towards 

 their free ends, and inflated at the opposite extremity ; a cuticular 

 lamina covers the inner surface. At its posterior end the wall of the 

 bulb is deeply plicated longitudinally, and its epithelium is in con- 

 tinuity with that lining the sac proper ; the posterior denticles of the 

 dart fit into some lateral diverticula of the cavity ; the inner surfaces 

 of all the cavities are, further, minutely pitted. At the anterior end 

 the wall of the sac presents a gap below by which its cavity com- 

 municates freely with the vestibule. In addition to its internal 

 epithelium, the connective tissue, and muscular layers, the sac has a 

 second connective- tissue layer, covered by an epithelial one, outside 



* Atti Soc. Toscana Sci. Nat. (IMcm.), iv. (1880) pp. 203-25 (2 pis.). 



