GODWIN-AUSTEN : iJVtPORTANCE OF ANIMAL IN LAND MOLLUSCA. 35 



For my Presidential address, I have therefore thought a few 

 instances of evolution that have come under my observation might 

 interest the members of this society, evolution being certainly one of 

 the most absorbing branches of natural history work. It will recall 

 at once to the minds of our members the work of Professor Darwin. 

 The great master's name will, this year, appear in the Presidential 

 addresses of many societies, both in this country and abroad, and it 

 must not be absent from the pages of our own. The memory and 

 labours of the eminent zoologist, to whom all naturalists owe so much 

 in stimulating research, has met with due honour this summer, the 

 great assemblage of scientific men at Cambridge, from every quarter 

 of the globe, testified most strikingly to the reverence in which his 

 name and work is held. 



The evolutionary stages I have to describe were noticed in certain 

 genera of the Zonitidae, a family which has an enormous tropical and 

 sub-tropical range, and is therefore one better known to those who have 

 collected in the east. Some well marked characters distinguish the 

 family one, viz. : the construction of the foot being remarkably 

 different from that of the Helicidse. Mr. B, B. Woodward very re- 

 cently in his Presidential address^ to the Malacological Society, when 

 referring to the work of Darwin, says very truly and tersely — " Every 

 organism possesses an inherent capacity to vary in a greater or less 

 degree in certain directions more or less peculiar to itself." This can- 

 not be better exemplified than in the diversity of form presented by 

 the extremity of the foot in the Zonitidse. The mucous gland varies 

 from being fiat, wide and open, or overhung by a lobe, which may be 

 short, curving over, or very elongate ; in other cases the foot is com- 

 pressed at the sides, keeled, truncate, the mucous gland a narrow slit, 

 or this last becomes very small and hidden by a lengthened fleshy lobe. 

 From South Africa, I have very lately received through the kindness 

 of two of our members, Messrs. Burnup and Ponsonby, a species with 

 the extremity of the foot quite unlike anything I have seen from India 

 or the Malay Archipelago. Thus more often a specific character, it 

 is in some cases of generic value. The next very variable external 

 character is found in the mantle, particularly in what have been called 

 the shell-lobes. To exemplify the various forms that these lobes 

 assume, I show in the Figures i to 3 those of the genera, A., A\ — 

 Macrochlamys; B. — Parvaiella; B\ — Euaustenia; C. — Cryptauste?iia; 

 D. — Austenia; E. — Girasia ; and F. — Crvptogirasia. In Macroch- 

 lafnys, which has a well formed coiled shell, these lobes are in the 

 earliest stage of development, they are more or less tongue shaped, 

 short, or extremely long as in M. petrosa (Fig. i Aa). 



Proceed. Mai. Soc, vol. viii., no. Si P- 275' 



