274 



HARDWICKE'S SCIENCE-GOSSIP. 



pered off with amazing celerity. One very large 

 mouse indeed, fat and audacious, seemed to be a sort 

 of Nabob among them, a tyrant, and evidently 

 capable of vigorously asserting himself. I happened 

 to be sitting quite still on a seat in this semi-wilder- 

 ness, when an apple fell from a tree. Instantly 

 several field-mice rushed from their holes, well 

 knowing evidently what the thud meant and made 

 for the apple, when lo ! the Nabob sallied out of his 

 hole. Off pelted the crowd to their retreats, where 

 they waited until this bloated aristocrat had had his 

 fill. He ate, until he evidently could eat no more, 

 and then left the rest of the apple as unworthy of any 

 further attention — retiring to his hole, doubtless 

 there to rest his well-gorged stomach. When he 

 had duly retired, the humbler members of the colony 

 darted from their holes, at the entrance of which they 

 had been watching the proceedings of " might 

 against right," and scrambled and pushed up against 

 one another to get a nibble of the remains of the 

 fruit. 



But this brings me to the main point. This 

 swarming of the field-mice arose from the destruc- 

 tion of the owls. Numbers of these birds used to 

 haunt the neighbourhood, and of course kept down 

 the mice. But from some reason or the other (I 

 fancy there was a superstitious feeling about the 

 poor bird), there had been a raid upon them, and 

 the destruction was so great that the neighbourhood 

 had been entirely ridded of them, and to the great 

 damage of the country around. So inveterate had 

 been the feeling against the owls, that the people 

 had not only killed the birds, but had carefully 

 sought out and destroyed their nests. It is some 

 time now since I was at Wildbach, but it was said 

 then, that it would be years before owls would 

 again frequent the place. Doubtless by this time the 

 inhabitants are wiser, though certainly sadder men. 



D. 



THE COLOURING AND BANDING IN LAND 

 AND FRESH-WATER SHELLS. 



MR. PACE'S criticism (p. 233, ante) on my 

 article published in the August issue is 

 amusing. I cannot help thinking that he could 

 have written it otherwise than as a jest. For what 

 he states he gives no references ; and in one or two 

 places it seems his bent to put different constructions 

 on words than what they were obviously meant 

 to convey. "As well as" — these were my words — 

 are plain J enough for the conception of the 

 simplest reader. The words "polar opposite" were 

 obviously not meant in any mathematical conception, 

 and to me they are more expressive than the words 

 "diametrically opposite." But the very words 

 which I have used have appeared in some recent 

 biological monographs with the same construction as 

 I placed upon them. To his tabulated statements 



my reply shall be brief, but to the point, and I shall 

 take them seriatim. 



(1 and 2.) Mr. Pace does not seem to know the 

 difference between the primary and the secondary 

 shell. I shall not here differentiate between them 

 more than I have previously done. I will not deny 

 that the organic matter of the secondary shell is com- 

 posed of conchyolin — in fact, I have laid consider- 

 able stress on this fact in my little volume on " Land 

 and Fresh-water Shells." But it is distinct news 

 that the plug in the shell-gland is composed of this 

 substance. Has Mr. Pace analysed these plugs, 

 minute as they are, and can he give us the differential 

 chemical analyses of conchyolin and chitin ? If so, I 

 wish he would give your readers the advantage of 

 such an advanced and intricate study. But I doubt 

 all such. And my reason for doubting is that the 

 late Francis Balfour, in the first volume of his " Com- 

 parative Embryology," says distinctly on p. 229 

 that the plug is a chitinous one. If Mr. Pace 

 will refer to this page he will find the following 

 words : " The shell-gland arises as an epiblastic 

 thickening on the posterior and dorsal side. In this 

 thickening a deep invagination is soon formed, in 

 which a chitinous plug may become developed 

 (Paludina, Cymbulia ? etc.), and in abnormal larvie 

 such a chitinous plug is generally formed." How- 

 ever, whether it is composed of chitin (which is more 

 probable), or its ally conchyolin (which is less 

 probable) does not invalidate my theory. All that 

 concerns the theory is that the plug is horn-coloured. 

 (3.) Necessarily I mean here all the fresh-water 

 species with which I am acquainted. Mr. Pace 

 could not have read my article very circumspectly, or 

 else he would have known that in it I specially 

 referred to British forms. He places against my 

 statement several foreign, and, in some sense, isolated 

 genera ; but I imagine that with the foreign species 

 other factors come into play, such as the one of low- 

 latitude given by Tryon, I believe on the authority 

 of Dr. Morch, in his " Structural and Systematic 

 Conchology." They, however, do not invalidate my 

 theory that they might have descended from horn- 

 coloured ancestors. The only two genera to which 

 he refers, and which have British representatives are 

 Paludina and Neritina. Of the first-named genus we 

 have two species, each of which has an unicoloured 

 and unbanded variety. Neritina Jlnviatilis — the only 

 species of the second-named genus in the British 

 fauna — has two unicoloured and unbanded varieties. 

 This at any rate is suggestive. An inspection of the 

 fresh-water specimens in the British Museum will 

 convince any one that horn-coloured forms are the 

 most frequent. Mr. Pace further wants to know how 

 it is that environmental conditions can be less in water 

 than on land. May I ask him how they can be equal 

 or greater? Unfortunately he gives no proofs of his 

 statement, and what I said is, I believe, acknow- 

 ledged as a working fact by our best evolutionists. 



