AGRIOLIMAX L^VIS. 123 



toiy organ, wliich differs from that of A. agrestis in being sliorter and more faintly- 

 grooved ; tlie PENIS-RETRACTOR is short, and arises from the lung-floor, considerably 

 in front of the heart and the kidney in the European form, but is usually absent in 

 L. campestris and its allies. 



The ALIMENTARY CANAL Somewhat resembles that of A. agrestis, but the INGES- 

 TIVE TRACT is Still shorter, and the rectum is quite free of any ciccal process ; the 

 SALIVARY GLANDS are slender and rather deeply lobed ; the liver is usually of a 

 pretty moss-o-reen colour; the right lobe forms the hinder end of the visceral mass, 

 the left lobe is also quite forward and divided into a number of slender points or tips. 



The RETRACTOR arises from the right side of the median line, behind tlie kidney, 

 from a bilid or trifid root, which after a longish course unites into a slender band 

 which furcates about mid- way ; the buccal retractors are quite slender and linear, 

 while the tentacular branches, though originating from the common stem as a 

 slender band, soon become very bulky. 



The MANDIBLE Or jaw is of the usual crescentic 

 form, witli less produced limbs and much more 

 prominent and convexly rounded rostrum or beak 

 than in A. agrestis; the colour is brown, darkest 

 along the upper margin and towards tlie extremi- fig. 135.— Mandible or jaw of 



ties of tlie lateral limbs; the cutting edge is also A. lavis, x 20. 

 finely serrate along its whole extent. (Armley, Leeds). 



The LINGUAL MEMBRANE is elongate, about three mill, long, and one mill, broad, 

 the transverse rows being arranged in arcuate form, bending distinctly backwards 

 towards the margins ; median row of teeth with well developed mesocone and ecto- 



FlG. 136. — Representative denticles from a transverse row of the lingual teeth of ^. Icrvis, X 240. 

 The animal collected at Horsforth, Leeds, and the palate prepared by Mr. J. W. Neville. 



cones ; laterals also tricuspid, the first and twelfth with endocone quite obsolete or 

 indistinct; marginals aculeate or with an ectocone more or less distinctly visible. 



The dental formula of a Horsforth specimen shows 



\% + il + -J- + iir + 1'2 X 1 1 5 = 6,555. 



Reproduction and Development. — The reproductive organs of 

 A. Iwvis, and to some extent those of the Llmacidw generally, have been 

 found by Dr. Babor to undergo a remarkable cycle of development, or 

 series of metamorphoses, during which the individuals of this species, vphich 

 are admittedly proterogynous, undergo a series of changes from their primi- 

 tively unisexual and purely female condition to the hermaphrodite state, 

 and afterwards become purely male by the atrophy of the female organs. 



These vFonderful mutations are demonstrated by the fact that most of 

 the individuals found in spring are unisexual with a purely female organi- 

 zation, possessing gonads yielding ova only ; later the examples show a 

 budding of the male organs, so that in summer and early autumn the 

 animals have become hermaphrodite, and present well developed organs of 

 both sexes. The evolutionary process, however, does not cease with the 

 full acquirement of the hermaphrodite state, as Dr. Babor has found that 

 after a certain interval the female organs may atrophy and dwindle away, 

 and the animal again become unisexual, but purely male, with gonads 

 secreting spermatozoa only. 



Even when the cycle is thus fully completed, it is not by any means 

 certain that in some species the sequence of transformations may not be 

 continued, and the rotation of sexes again take place. 



