242 



HARDWICKE'S SCIENCE-GOSSIP. 



presenting the phenomenon of atrophy of the pigment 

 glands ? 



(6.) By-the-bye, Helix aspersa var. exalbida, can 

 hardly be considered as a reversion to a white or even 

 horn-coloured ancestor, all the specimens I have seen 

 having a distinct tinge of yellow suffused over the 

 shell, while their light appearance seems to be due to 

 the absence of band colour, and the reflection of the 

 white nacreous interior through the yellow pigment. 



(7.) The idea that the " pneumo-chlamyd " 

 (Cyclostoma elegans) has evolved from a freshwater 

 form, is new to us, and the reasons for the assump- 

 tion would doubtless be interesting ; here again 

 Mr. Williams seems to overlook the fact that many 

 of the tropical Operculata are as brightly and 

 complexly coloured as the Hebrides. 



We now adduce a few facts and arguments to 

 make it clear that the colour of our Hyalinoe is not 

 necessarily due to the persistence of the primitive 

 horn colour, but is more probably due to the suffusion 

 of the darker band colours, as suggested in this 

 magazine by Mr. T. D. A. Cockerell ; * also that 

 colour has not always evolved along a course leading 

 from the simple to the complex, and there is strong 

 reason for believing that Mr. J. W. Taylor's 

 supposition "that Helix cantiana, cartusiana, etc., 

 were once banded species," f is tenable. Few facts, 

 so far as I am aware, have as yet been published in 

 support of these views, and this must serve as my 

 apology for the following : — 



(i.) Helix cantiana, a horn-coloured variety, often 

 has the five bands distinctly, though faintly developed, 

 and may be more legitimately regarded as a reversion 

 to a banded ancestor, than the occurrence of albino 

 specimens. 



(ii. ) When the brown colour of Helix memoralis is 

 suffused over the shell as in the var. castanea, the 

 interspaces between the bands are lightest in colour ; 

 one specimen presenting the above features, has the 

 umbilical region clouded with continuous brown ; 

 this tendency of the band colour to pervade the 

 umbilical region is noteworthy as it becomes normal 

 in Helix cantiana. The interspace between the third 

 and fourth bands is often the lightest part of the 

 shell, forming a marked light band, in some speci- 

 mens of H. nemoralis var. castanea, and this is 

 clearly shown in specimens with a band formula 

 (1 2 3K4 5).- Now careful comparison leaves no 

 doubt that the white band developed around the keel 

 of Helix rufescens, IT. cantiana, H. cartusiana, H. 

 concinna, and H. hispida corresponds, not to band 

 No. 3, as I believe is generally supposed, but to the 

 interspace just below it and above band No. 4. 

 This relative position may be exactly determined as 

 band No. 4 is bisected by the suture of the lip in 

 H. nemoralis. 



* SciENXE-Gossir, January, iS88, p. :o. 



+ Valedictory address as President of the Conchological 

 Society, 1887, published in "Journal of Conchology," April, 

 1888. 



(iii.) It is now necessary to show that when white 

 is abnormally developed in Helix, it occupies the 

 interspaces, or in other words affects the suffused 

 ground colour. A variety of Helix hortensis from 

 Bourne End, Bucks, having white around the 

 sutures, traces of white between the bands (that 

 between Nos. 3 and 4 being most developed), and 

 white continuous over the umbilicus, while the 

 positions occupied by the bands are of a light apple- 

 green tint, admirably illustrates this. Again, fifteen 

 specimens of Helix lapicida var. minor, from Allport, 

 Derbyshire, are of the suffused dark brown colour. 

 Careful examination reveals the following differentia- 

 tions possibly bearing on their evolution : Traces of a 

 darker brown band in the position of No. 3 are 

 exhibited by four specimens ; seven have traces of 

 No. 4 only ; one has, in addition, a thin silvery 

 streak occupying the interspace immediately above 

 the band No. 3 ; another has a thin streak im- 

 mediately below band No. 4, while the two other 

 specimens have thin silvery streaks in the same 

 relative positions but no bands. 



(iv.) The umbilical regions of Hyalina cellaria, 

 alliaria, and nitidula are often clouded with white, 

 which in some specimens ends off with regularity and 

 sharpness of definition just about the region of the 

 fifth band : this becomes intelligible in the light of 

 the above facts as representing the original ground 

 colour, while the brown corresponds to the suffused 

 bands ; and this view receives strong confirmation 

 from the specimen of Hyalina nitidula (figured and 

 described by Mr. T. D. A. Cockerell in Science- 

 Gossip, October, 1888, pp. 205-6). 



(v.) The explanation given by Mr. Williams of the 

 occurrence of horn-coloured shells in our Hyalinse is 

 unsatisfactory, because it would be extremely difficult 

 to prove their relative immunity from the attacks of 

 those animals which make snails their food, while it 

 is easy to show that they have many enemies ; among 

 which may be enumerated, thrushes, blackbirds, 

 starlings,* shrews, f and probably ants, J and if their 

 small size protects them, how much more would the 

 size of Helix acztleata and Helix pygmcea preclude the 

 necessity of their environmental and protective 

 coloration ? 



POND-HUNTING. 



I HAVE thought it might be interesting to micro- 

 scopical amateurs who may be readers of your 

 magazine, to know what wide fields of investigation 

 are open even to those whose opportunities for 

 country excursions and pond-hunting are extremely 

 limited, and who, for this reason, may be dis- 

 couraged from following up this most fascinating 

 branch of study. They may be glad to learn that 



* Tate in " Plain and Easy Account of the Molluscs," p. io5. 

 + SciENCE-Gossir, January, 1884, p. 3. 

 % Ibid., April, 1884. 



