HA RD WICKE'S SCIENCE- G OS SI P. 



281 



seven L. siagnalis in the course of one afternoon. 

 The beetles also ate L. peregra, but seemingly with 

 not so much gusto as they did stagnalis, for, on 

 placing equal quantities of these two species into the 

 aquarium, they fixed the latter species first. They 

 were conchologists, too, in this respect, for they 

 evidently knew Z. stagnalis from Z. peregra. And 

 this is of importance to note, since from this observa- 

 tion (and others I tried with like results), it is 

 legitimate to conclude that, in any given locality, the 

 number of Z. stagnalis and Z. peregra will decrease 

 as the number of dytisci increase, the former species 

 decreasing more rapidly than the latter. I may be 

 permitted to say that it is one of the faults of our 

 shell-specialism that we do not sufficiently attend to 

 the relation of other groups to our own group of 

 study, and hence chorological matters are but 

 indifferently understood. I may be permitted to 

 draw the attention of shell-faunists to this point, 

 and to ask that the subject of snail-enemies may have 

 a fuller attention given to it than has hitherto 

 obtained. One genus of leeches, the glossiphonia, to 

 which I believe scarcely any attention has been paid 

 in England for the last twenty years, must act as a 

 very great factor in decreasing the number of aquatic 

 and palustral molluscs in a locality where they 

 abound, and I would suggest that conchologists pay 

 some attention to the number of these snail-eaters 

 present in localities of which they are making a faunal 

 report. — J. W. Williams. 



The Meaning of Cygnea in Anodonta 

 Cygnea.— On p. 189, Mr. F. P. Perks asks why 

 the specific names of Cygnea was gi%'en to this mussel ? 

 There is no superstition connected with it, as sug- 

 gested, as with the barnacle and the goose. I believe 

 Linne gave it this name because he considered it the 

 favourite food of swans. — J. IF. Williams. 



The Darts of Helicid.^. — In my note on page 

 213, concerning crystalline stylets printed under this 

 heading, I state that in no morphological text-book 

 does a mention occur of any crystalline stylet being 

 found in the Mollusca except in the Unionacea. As 

 I have been written to concerning this statement, 

 and in order to avoid any further misapprehension, I 

 should like to say that I only referred to English 

 inland forms when I used the word "Mollusca," to 

 the exclusion of marine species. — y. IV. Williams. 



Discovery of Pupa cinerea in Lancashire. 

 —(Peculiar to the basin of the Mediterranean, 

 J. M. Taylor).— The appearance of this stranger to the 

 British fauna was again verified for the fourth time 

 on the 30th of October last by Mr. J. Jones of 

 Church, who brought a beautiful specimen to the 

 monthly meeting of the Accrington Naturalists' 

 Society on the second day of November. The four 

 takes have been obtained at intervals extending over 

 a period of twelve years, and though doubts have 



been expressed by some of our leading conchologists 

 concerning this northern habitat, and whose un- 

 willingness to include a spurious species dfeserve the 

 highest praise, nevertheless facts must drive doubt 

 away. The best vindication of its occurrence was at 

 a field-day excursion of the society about four years 

 ago, when the take was witnessed by several of the 

 members, and by them considered a small reversed 

 form of Claiisilia laminata ; but subsequently a couple 

 of the shells coming into my possession about eighteen 

 months ago they were sent to J. M. Taylor, of Leeds, 

 who pronounced the species Pttpa cinerea, but was 

 somewhat unwilling to give it a place in the British 

 list, as no live ones could be obtained setting the 

 matter beyond doubt. But convinced in my own 

 mind of the accuracy of the find, I determined to visit 

 the locality myself, and did so last year, and also in 

 August of the present year, the result in both cases 

 being unsuccessful. But hearing of the whereabouts 

 of the late Mr. W. Cooper's collection, which was 

 sold to a gentleman in Church parish, I resolved 

 upon gaining access to that collection ; and as 

 Mr. Cooper and Mr. Jones took it at the same time 

 in the first instance, and as this test was an impor- 

 tant matter, I was fortunately rewarded in finding 

 nine beautiful mounted specimens. Mr. Jones again 

 found it in the same spot, which is situated in a 

 well-wooded, out-of-the-way-place, where foreign 

 wood or plants or any kind of foreign importations 

 are not likely to have ever occurred. There 

 appears, therefore, no probability of its introduction, 

 and we do not hesitate to call it a British species. — 

 Robert Wriggles-worth. 



t 



NOTES AND QUERIES. 



Regulation and Distribution of the 

 Electric Current for Lighting Purposes. — 

 Before the current produced by the generator can be 

 used to do the required work, it is necessary to see to 

 its regulation and distribution. The due regulation 

 of the current is of as much importance as the 

 adoption of suitable generators and receivers, i.e. the 

 apparatus which produces, receives, and consumes 

 the current, such as lamps, motors, or decomposition 

 cells. To work with unregulated currents is far from 

 economical, and often causes considerable loss, as may 

 be shown by the following example : Suppose the 

 currents of a machine to have a strength corresponding 

 to the number of lamps which they are supposed to 

 feed. Now suppose that all of a sudden, either by 

 chance or purpose, a number of lamps are put out, at 

 once the resistance in the circuit is considerably 

 diminished. The current being inversely proportional 

 to the resistance, it follows that the decrease of 

 resistance causes increase of current, which will not 

 only alter the remaining lamps, but might injure the 

 insulation of the machine, or melt off portions of 

 metal. To prevent cases like this occurring, the 

 generator may be constructed so as to allow to pass 

 only currents of such strength as are wanted, or 

 regulators constructed for the purpose may be used. 

 Finally, the receivers, i.e. the lamps, may be so 

 arranged as to allow only the required current to 



