THE CAKNIVOROUS SLUGS OF SOUTH AFRICA. 179 



most distinct. Each lobe is again subdivided into a number 

 of lobules, the arrangement of which varies in different 

 individuals. The left division of the liver lies entirely to the 

 left of the intestine, and is about equal in size to the right. 

 It also is divided and subdivided into lobes and lobules, but 

 not so distinctly as is the right division. 



In Apera dimidia the liver is also divided into two main 

 divisions, one right and anterior, the other left and posterior ; 

 and, as in the other species, these divisions have separate 

 ducts. They are not, however, quite so distinct from each 

 other as in the species mentioned above, and they both 

 receive their blood from a single branch of the anterior aorta, 

 the so-called posterior aorta being absent. Moreover, the 

 disposition of these divisions with regard to the intestine is 

 quite different to that which I have described as character- 

 istic of A. gibbonsi, A. parva, A. burnupi, and A. sex- 

 angula. The anterior or right division lies above the crop, 

 entirely in front of the intestine, while the posterior or left 

 division, which is divided into two lobes, occupies a position 

 corresponding to that held in the other species by the two 

 posterior lobes of the right division of the liver (PL XXI, fig. 

 132). This fact suggests that possibly the whole of the liver 

 of A. dimidia corresponds to the right division of the liver 

 in the other species. If this theory be correct, it would 

 explain, not only the anomalous position of the liver with 

 regard to the intestine in A. dimidia, but arise its still more 

 surprising blood-supply. We would have to suppose, however, 

 that the origin of the branch of the right hepatic duct coming 

 from the anterior lobe had shifted inwards as far as the intes- 

 tine itself j but this might have been caused by the greater 

 separation of the lobe due to the lengthening of the right 

 division of the liver as it came to occupy also the position of 

 the left division. And this separation of the tAvo principal 

 branches of the hepatic duct would be merely a case of rever- 

 sion, for H. Fischer^ has shown that each division of the liver 

 was probably originally subdivided into two or more lobes, 

 ' • Bull. Sci. France et Belg.,' 1892, vol. xxiv, p. 331. 



