226 INTRODUCTION. 



der, to form the vagina. In H. concava and H. multi- 

 lineata, the neck is long, dilated at its lower part, and 

 strongly muscular, and its internal surface presents a 

 number of longitudinal rugae. In H. profunda and S". 

 fuliginosa, it is long, cylindrical, and strongly muscular. 

 The genital bladder, constantly existing, presents con- 

 siderable variation in the form, size, and length of the 

 duct. It is generally subrotund, oval, or pyriform in 

 shape, and large. In H. solitaria the duct is wide, as 

 long as the oviduct, and dilated at its lower part. In H. 

 jperspectiva it is as long as the oviduct, and narrow. In 

 E. alternata, H. ligera, H. intertexta, IT. concava, H. 

 snppressa, and H. gularis, it is rather more than half 

 the length of the oviduct. In the remaining species gen- 

 erally, the bladder reclines upon the lower part of the 

 prostate gland, and its duct is about the length of the 

 neck of the oviduct. In II. vmltilineata it does not 

 reach the prostate gland, and so gradually passes into its 

 duct as to be a mere, long, coecal tube. In H. her- 

 landeriana the duct of the bladder is as short as that of 

 Arion. Usually, the surface of the bladder is smooth ; 

 in H. profunda and H. exoleta it is transversely folded ; 

 in H. fuliginosa it is regularly, longitudinally folded. 

 In H. concava and H. multilineata, the duct of the 

 bladder at its termination dilates, and is strongly muscu- 

 lar. In H. solitaria the lower third is dilated. In E. 

 fuliginosa and ff. p)rofunda, it is strongly muscular the 

 greater part of its extent. In H. albolabris, H. palliata, 

 H. tridentata, etc. it is dilated to the size of the bladder, 



