ANATOMY OF PALUDBSTRINA 179 



frequently into two parts which occupy more or less opposite 

 sides of the vagina and, where they meet, show a certain 

 amount of transition in their structure. 



One portion is usually stained in haematoxylin and eosin 

 a vivid light purple in which the pink tinge predominates. 

 It consists of two kinds of cells. A layer of ciliated, cubical 

 cells lines the cavity of the gland. Some of them are drawn 

 out into irregular, elongate extensions with which are asso- 

 ciated other rather elongate cells. These form irregular 

 digitiform glandular masses. A distinct lumen is seen in these 

 masses (Text-fig. 10). It is uncertain how they pass their 

 secretion to the exterior, as I have never observed a com- 

 munication between the lumen and the exterior. The second 

 area usually stains a deep purplish blue with the same stain. 

 Seen in its most characteristic form it is composed of the same 

 columnar ciliated cells and an inner glandular mass. The latter 

 is more compact, the nuclei of the constituent cells are fewer 

 and often arranged at the periphery of rudely quadrate masses. 

 One is tempted to conclude that this second portion only 

 represents another stage of the condition observed in the first 

 described part, and that in the one the cells are full of secretion 

 and tend to obscure a structure like that described in the first 

 case. In the compact portion it is very hard to make out cell 

 outlines, and certainly nothing like the digitiform glandular 

 processes can be seen. It is, on the other hand, very certain 

 that in certain areas transitional masses are to be found. 



I am inclined on the whole to consider that there are two 

 functionally distinct portions of this gland mass, though inter- 

 mediate stages are found. A comparison may be made with 

 the rather similar structure of the accessory glands (ootype, shell- 

 gland, &c.) of Neritacea which have been described by Bourne (3). 



The cavity of the vagina is continuous with those of the 

 glands. 



(3) Male Organs (Text-fig. 11). 



The testis consists of a number of branching follicular tubes 

 and in general plan resembles the ovary. Only one kind of 



