HELIX CARTUSIANA AND HELIX SYRIACA : 



Their Relationship and its Probable Significance. 



J. W. TAYLOR, M.Sc. 



Helix ( Thcba) syriaca as evidenced by specimens from 

 Samos, near Smyrna, and Mount Carmel, Palestine, for which 

 I am indebted to Mr. J. R. le B. TomHn and Rev. Canon 

 Horsley respectively, indicate that though undoubtedly closely 

 allied to our British H. cartnsiana, still show sufficient diver- 

 gence to entitle it to an independent status. 



The H. syriaca is characterized by the usually total closure 

 of the umbilicus, by the comparatively distinct reticulate 

 whorl-sculpturing, the somewhat flatter basal peristome, and 

 the presence of a broad and distinct darker band above the 

 periphery with a similar though less persistent one beneath, 

 separated by a white, calcified, peripheral zone. 



On the other hand, the West European and Mediterranean 

 examples of H. cartusiana show a white or whitish shell, 

 frequently clouded about the aperture with brown, but oc- 

 casionally showing faint vestigial traces of a white and some- 

 what cretaceous peripheral band. 



The Samos and Samarian shells demonstrate and confirm 

 the accuracy of the explanation that the feeble indications 

 of the somewhat opaque peripheral zonulation in H. cantiana 

 H. cartusiana, etc., are the relics of the white and calcified 

 space separating the formerly existent upper and lower 

 group of bands, which have been lost by those species, but are 

 still retained by H. syriaca. 



This palpable relationship of our H. cartusiana with 

 H. syriaca displayed by the retention of the primitive band 

 arrangement by the latter, is indicative of their phylogenetic 

 affinity, and the truth of the axiom laid down by the immortal 

 Darwin that new species arise because the differences they 

 acquire confers some advantage over the more primitive 

 forms from which they have arisen, and that they will therefore 

 inevitabty crowd out and supplant their progenitors from the 

 active evolutionary area and compel their migration to other 

 regions. 



We are thus led to the conclusion that — Europe being 

 probably the original source and metropolis of the most 

 advanced forms of life and the area of the greatest development 

 and concentration of the central nervous system, while a de- 

 creasing degree of dominating power is demonstrable as we 

 recede towards or beyond its confines, so that the oldest or 

 most primitive forms, if not isolated in undesirable regions, 

 are necessarily the farthest removed from the original home 

 of the groups. 



1918 Jan. 1. 



