THE CARNIVOROUS SLUGS OF SOUTH AFREGA. 189 



148, 149); in A. gibbonsi, A. parva, and A. diniidia 

 it is shorter and generally broader (figs. 143, 144, 146, 147). 

 In some specimens the female or oviducal portion is greatly 

 swollen, as in the example ofA.dimidiaof which the repro- 

 ductive organs are shown in fig. 147. The free oviduct is 

 rather long and narrow, and is directly continuous with the 

 vagina, which is also rather narrow but usually somewhat 

 shorter. The vestibule or genital atrium is extremely short. 



The Receptacdlum Seminis and its Duct. — The sperma- 

 theca or receptaculum seminis is an oval vesicle, situated, in 

 A. parva, beside the anterior end of the free oviduct, the 

 receptacular duct in this species being exti-emely short 

 (fig. 146). In the other forms the receptaculum seminis 

 lies against the anterior end of the common duct, and the 

 length of the receptacular duct is therefore about equal to 

 that of the free oviduct, since the anterior opening of the 

 receptacular duct marks the junction of the free oviduct with 

 the vagina. In Apera gibbonsi the receptacular duct is 

 a simple narrow tube (figs. 144, 145). In A. sexangula it 

 becomes swollen towards its union with the vagina, so that 

 the anterior part of the duct is fusiform (fig. 149). In A. 

 burnupi the anterior part of the duct is still more swollen 

 (fig. 148). Lastly, in A. dimidia the swollen end of the 

 duct has become attached to the adjacent part of the body- 

 wall by a number of muscles on each side (fig. 147). And 

 as we pass up this series the receptaculum itself becomes 

 progressively smaller, and it seems as though the receptacular 

 duct were taking its place. If this tendency were to proceed 

 still further we should have a vesicle which would be indis- 

 tinguishable from a sessile receptaculum seminis, although in 

 reality it was the swollen anterior end of the receptacular 

 duct, the rest of the organ having disappeared. Possibly 

 this may have happened in some of the genera which are 

 usually described as having a sessile receptaculum. 



The Male Organs.— The vas deferens arises from the 

 anterior end of the common duct, and passes forwards close to 

 the free oviduct and vagina as far as the vestibule. It then 



