282 PROCEEDINGS OF THE MALACOLOGICA.L SOCIETY. 



shell in the nepionic stage and becomes similar to Patella, a depressed, 

 straight cone in the neanic and ephehic stages, the habitat being like 

 that of Patella and the approximate forms of Saliotis and others, 

 comparatively sedentary upon littoral rock ledges." Jackson, too 

 {IfS, p. 294), who had the benefit of Hyatt's direct teaching, refers 

 the uncoiled stage of Vermetus to the ephebic or adult period, and 

 therefore by no means considers it gerontic. 



So far, then, as the Gastropoda are concerned, we are but on the 

 threshold of inquiry, and there is need of much further work among 

 other groups and especially the older fossil forms. 



The chief object in thus drawing attention to such progress as has 

 been made in the study of molluscan phylogeny and in emphasizing 

 the fact that so much more of very great interest remains to be done, 

 is the hope that some members of this Society may be persuaded to 

 take up this branch of investigation, hitherto comparatively neglected 

 in England. Opportunitj', of course, Avill not come to all, but for 

 willing workers other less comprehensive fields of research connected 

 with the question are equally open. As an example may be instanced 

 the excellent work done quite lately by Mr. E. S. Hussell in studying 

 the Limpet. 



In his memoir (55), after narrating the results of experiments on 

 the well-known homing propensities of this mollusc, that demonstrate 

 large Limpets to be moi'e fixed in their positions than small ones, 

 Mr. Russell turns to the influences of environment on the size and 

 character of the shell. He finds that the shells of Ihose Limpets 

 which live near high-water mark are at every stage of their growth 

 higher spired and a little broader, though narrower in proportion to 

 their height, than low-water shells. Also the proportion of large 

 shells is greater at high-water than at low-water sites. When those 

 inhabiting exposed are contrasted with shells in sheltered spots in 

 a given definite locality, the former are found to be proportionately 

 narrower than the latter. Observation showed that of the two types 

 of shell, the rough and the smooth, the first-named were attached to 

 rough, the others to polished stones, and were simply the result of the 

 growing shell-margin moulding itself to the surface of attachment, so 

 that the two types are the outcome of a single environmental character. 



Similar observations are now required with respect to other inter- 

 tidal molluscs.^ The effect of environment on molluscs is as yet 

 but very iiuperfectly understood. Beudant's experiments (4) on the 



^ At a meeting of the -Challenger Society held on January 27th of this year, 

 Mr. TV. M. Tattersall gave some exceedingly interesting details concerning 

 the breeding habits and development of the British species of Littorina. It 

 appears that the eggs of L. littorea are deposited in small capsules shaped like 

 a Panama hat, and are not attached, which accounts for their not having been 

 recorded hitherto. The species is exposed only at low spring tides, and the 

 embryo is freed as a trochosphere, later attaining the veliger stage ; the embryo 

 of L. obtusata, which is exposed at ordinary low water, is freed as a veliger ; 

 L. rudis and L. neritoides, on the other hand, which live at the high-water line, 

 are viviparous. A remarkable instance this of adaptation to suit environmental 

 conditions. (Cf. Athcnmim, February 13th, 1909, pp. 203-4.) 



