July 



NATURE 



273 



asks how I manage to direct that energy along a definite path so 

 as to produce a willed result. The only answer I know is, " By 

 a nervous impulse liberated from brain centres." But what is it 

 that is thus liberated ? and what pulls the trigger to liberate it ? 



By mechanical analogy one would say that energy can only be 

 guided by force, and that force must therefore be exerted in the 

 brain cells ; but, if so, the relation between force, which is a 

 mechanical thing, and will or life, or whatever it is, which is a 

 psychological thing, demands investigation. 



I trust that Mr. Lloyd Morgan will help me to get my ideas 

 on these subjects straighter, and will point out if I have made 

 any assertions which are obviously erroneous or grotesque. The 

 borderland of psychology and physics is the last place in which 

 I would like to dogmatize ; and in a letter like this I see no harm 

 in airing confessedly immature and groping notions, in the hope 

 that ventilation may clear the air. So far as physics only is con- 

 cerned, I have stated how I regard the phrase "expenditure of 

 energy " in the Philosophical Magazine for June 1885 



With regard to the crux raised in Mr. Dixon's last paragraph, 

 that nothing but matter can exert force, because the acting matter 

 must receive an equal opposite momentum, it may perhaps be 

 just worth noticing that an infinite mass can absorb any amount 

 of momentum without receiving a trace of energy or being itself 

 in any way affected. Oliver J. Lodge. 



Liquid Prisms. 



I OBSERVE in Nature of July 2 (p. 207), that it is stated Herr 

 Wolter has recently recommended o-monobromnaphthalene as a 

 substance peculiarly fitted for study of the ultra-violet part of 

 the spectrum, by reason of its high dispersive power and trans- 

 parency for the ultra-violet rays. 



Perhaps I may be permitted to state that Mr. Madan pub- 

 lished an account of its dispersion and refractive power in the 

 Phil. Mag. , and recommended its use in liquid prisms. Having 

 made use of many other substances, including methyl salicylate, 

 I gave this a trial. For ordinary work it would be excellent if 

 colourless ; but unfortunately, no matter how free from colour it 

 may be when freshly prepared, long-continued use causes it to 

 become yellow, and in considerable thicknesses even dark brown. 

 For the ultra-violet rays it is undoubtedly better than carbon 

 disulphide, but nevertheless practically useless, as the line N, 

 which it is said to transmit, has a wave-length of 3580, so that 

 only about one-half of the ultra-violet solar rays are observable 

 with it. In metallic spectra almost all lines of interest lie 

 between 3580 and 2000. A liquid which I considered to possess 

 much superior optical properties is mercuric niethide ; it is per- 

 fectly colourless, and of such density that flint glass will float 

 upon it. When the glass is immersed it becomes invisible, 

 consequently the refraction and dispersion of the liquid are 

 probably exceptionally high. As far as I can recollect, being 

 without access to my notes, a thickness of 50 millimetres freely 

 transmitted all rays to about K 2900 — that is to say, the entire 

 olar spectrum. Unfortunately, it has its drawbacks, in being 

 -omewhat volatile, and its vapour highly poisonous. 



Stonehaven, N.B. W. N. Hartley. 



The Identification of Templeton's British Earthworms. 



Between the years 1829 and 1836 the first series of Loudon's 

 Magazine of Natttral History appeared in nine volumes. In the I 

 last volume we find some notes on earthworms by Templeton, 

 which have proved somewhat puzzling to students of more recent 

 times. I have been fortunate enough to follow Templeton in 

 some of his researches, and am able to correct and verify certain 

 of his statements. 



The Lumbricus \anthurus, Temp. {op. cit., ix. 235), is the 

 angler's gilt tail, and as such is synonymous with Lumbricus 

 f'uter, Hoff'm., and Dendrobcena Boeckii, Eisen. Lumbricus 

 i^ordianus. Temp. {loc. cit.), is undoubtedly the mucous worm 

 (Allolobophora mucosa, Eisen), or one of its near allies, all of 

 which are to be found of a pale rosy colour coiled up into a knot 

 at certain times of the year. 



It is to Lumbrictis omilurus ( = Omiluriis rubescetis. Temp., /c?^. 

 £il.), however, that I wish to direct special attention. Grube, in 

 1851 (" Familiender Anneliden,"p. loi), placed it, with Temple- 

 ton's other worms, in a list of species which were insufficiently 

 characterized for systematic purposes. Vejdovsky, in 1884 

 (" System und Morph. der Oligochaeten," p. 62), places it among 



NO. I 134, VOL. 44] 



the questionable species without note or comment, and, so far as 

 I can gather, no one has been able to throw light upon it since. 



Templeton says the worm is never larger than half the size of 

 Z. terrestris, L., is of a bright reddish-brown, with the tail very 

 flat, and the body unfurnishfd -vith a belt at the position of the 

 sexual organs. It would be very easy to suppjse from this 

 somewhat vague account that the writer had only seen immature 

 specimens ; but a little careful study of his words shows that he 

 knew what he was writing, and that his worms were mature. 

 Now a mature species of Lumbricus without a clitellum is 

 certainly an anomaly, and needs investigation. 



While collecting Annelids recently, I came across half-a-dozen 

 specimens which at first sight exactly resembled Lumbricus rubel- 

 lus, Hoff'm. I took them home for verification, and immediately 

 observed the difference. I had obtained with them typical 

 specimens of rubellus, which enabled me to make a careful com- 

 parison of the two species in a living state. 



The following is a description of the worm as I wrote it down 

 before observing Templeton's account. 



Colour dark brown, iridescent on the dorsal surface anteriorly, 

 becoming lighter towards the posterior extremity, which is flesh- 

 coloured or light red, pink ventrally. Prostomium dovetailing 

 completely into the peristomium, and possessing a transverse 

 groove in the middle, as shown in the accompanying sketch. 



Lumbricus ruhcscens. Segments i to 3 with prostomium entirely cutting 

 the first segment or peristomium. 



Segments not annulated (or divided by transverse rings). 

 Length about 3 inches, total number of segments about 120. 

 Setae in couples as in typical Lumbricus. Male or spermiducal 

 pores on segment 15 with papilla?, which, however, do not 

 extend over the neighbouring segments. Body cylindrical in 

 front, flattened posteriorly. The dorsal pore between 5 and 

 6. It appeared at first between 7 and 8, but by using 

 polarized light on the cuticle when spread on a glass slip the 

 whole series of pores in one or two specimens became clearly 

 visible from the fifth segment backwards. 



On the ventral surface prominent papillae appeared on seg- 

 ments 28 and 29, such as are often seen on typical L. agricola, 

 Hoffm. Now came the crucial question, Is there no clitellum ? 

 By studying all the examples carefully, I found that they agreed 

 in one particular. The segments 34 to 39 differed in structure 

 from the rest on the dorsal surface On the under surface from 

 33 to 40 were differentiated, and showed a glandular structure, 

 while the band representing the tubercula pubertatis extended 

 distinctly along the ventral surface of 35, 36, 37, 38. 



This description of the external characters shows the worm to 

 be a decided Lumbricus, tested by Dr. Benham's definition in 

 '•An Attempt to Classify Earthworms"; but it differs from 

 ever)' one of our British species, especially in the backward 

 position and inconspicuous nature of the clitellum. I am unable 

 to refer it definitely to any of the European species, and propose 

 that for the present it should be known as Lumbricus rubescens 

 (Temp.), thus retaining the two names from Templeton's 

 synonyms which are most appropriate to what I regard as the 

 species intended by him. 



I may add that I have recently found one or two other earth- 

 worms in Yorkshire which have not yet been recorded as British, 

 and will form interesting additions to our Annelid fauna. 



Idle, near Bradford, July 15. Hilderic Friend. 



Copepoda as an Article of Food. 



During recent years a good deal has been said amongst 

 marine zoologists of the use, as a food supply, that might be 

 made of the enormous numbers of Copepoda that swarm in the 

 surface-waters of the sea, and the Prince of Monaco has pointed 

 out the value this widely-distributed nuiritious matter might 

 have to shipwrecked sailors ; but I am not aware that anyone 

 has yet actually made the experiment of cooking and eating 

 Copepoda, so the following record may be of some interest. 



