Oct. 27, 1887] 



NATURE 



605 



detached. The fish, Seriola, was kept alive until the larger 

 buds of the grape-like gonosomes separated from the hydroids. 

 These buds are medusae, different from any which I have ever 

 seen, but with close affinities to common and well-known genera. 

 A large glass aquarium containing several gallons of water was 

 found to be swarming with these medusae two days after the 

 capture of the Seriola. 



Each fully-grown medusa closely resembles the genus Sarsia. 

 It has an oval bell, four broad unbranched radial tubes, and four 

 long simple tentacles. There are no octocysts on the margin of 

 the bell. 



If the strange form of the hydroid was not known to me, it 

 would have been very easy to call this medusa a near relative of 

 Sarsia. The medusa belongs to a group, called by Agassiz 

 the Tubularians, but its hydroid is different from that of any 

 other member of the group. 



One other parasitic hydroid may be thought to be related to 

 Hydrichthys. I refer to the Polypodium, described from the 

 ova of the sturgeon. A description of Hydrichthys with figures 

 of the fish (Seriola) to which it is attached, and of the hydroid 

 with its medusa, will soon be published by me. As a discussion 

 of its relation to other hydroids has little interest except to a 

 specialist in the study of medusae, a comparison of Hydrichthys 

 with Polypodium and other genera is reserved until my complete 

 diagnosis of the genus and species. J. Walter Fewkes. 



"Cambridge, Mass., U.S.A. 



Music in Nature. 



In Nature for August 11 (p. 343) there is an interesting 

 rticle on music in Nature ; the writer evidently being inclined 



deny that true musical notes, and especially several notes in 

 Succession having a musical relation to one another, can be found 

 in bird songs. However this may be in the Old World, we have 

 in the New at least one example of a bird which not only sings, 

 or rather whistles, pure and well-sustained musical notes, but 

 has a succession of notes with such intervals as to form a simple 

 melody. I refer to the scarlet tanager. 



While we were at The Thousand Islands early in the summer 

 of 1886, one of these brilliant fellows carried on a courtship among 

 the trees close to our cottage, repeating incessantly during the first 

 two days that we heard him the following strain, 



in a clear, bright whistle. After the first two days he changed 

 his song thus : — 



Es^^1|3=eS^33: 



and during the three weeks that we heard him he made no other 

 variation, except that he occasionally repeated the last two notes 

 a third time, thus fillin^j out the bar. The notes were taken 

 down by a trained musician, and if whistled give the tanager's 

 song exactly. 



It may be mentioned that, though perhaps the most brilliant 

 in plumage of our Canadian birds, the male tanager referred to 

 made no attempt at concealment, but swept like a living flame 

 from tree to tree close to the cottage, and when singing preferred 

 to sit on the topmost bough of a pine near by. 



A. P. Coleman. 



Faraday Hall, Victoria University, Cobui^, 

 Ontario, October 8. 



Swifts. 



The following facts relating to the habits of the swifts were 

 observed by paying close attention to these remarkable birds 

 daring the past summer. For more than a month, i.e. from 

 June I to July 12, we watched them here. On the fine evenings 

 about forty of them (th? males I believe), ascended high into 

 the air at about 9 o'clock, and after wheeling about for a 

 minute or two, screaming loudly, fled straight away, sometimes 

 in one direction, sometimes in another. White, in the " Natural 

 History of Selborne," notices that : "Just before they retire 

 whole groups of them assemble high in the air, and squeak and 

 shoot about with wonderful rapidity." But the most wonderful 



part of the proceeding is that they do not come down again that 

 night. At all events I can show that they do not come down 

 again before 10.30, at which time I do not think they would be 

 able to find their nests under the eaves of the church. Between 

 the dates above-mentioned there were only six days during which 

 I did not see or hear the swifts ascend and fly off. Three of 

 these days were rainy, and the swifts stayed at home, and on 

 three other days I was not able to watch them. The church- 

 yard adjoins the garden of this house, and numbers of swifts 

 build in the church, which is but a few feet from where we sit 

 out and walk about in the summer evenings. 



After seeing the high-flying swifts safely off to the south-west 

 at 9.10 one night, I sat on a tombstone under the north eaves 

 where most of them build, until 10.30. Two swifts hawking 

 low for flies entered their nests after 9. 10, but one of them was 

 flying low while the high-flyers were in sight, and the other came 

 out of its nest after they had gone, and both had retired before 

 9.20. On the other side of the church my father (the vicar) and 

 my brother, who both took a keen interest in the d iings of the 

 swifts, were keeping watch alternately, and only two low- flyers 

 were out there after the others had gone. The high-flyers did 

 not return. On several other nights we watched until II 

 o'clock, though not quite continuously, but quite closely enough 

 to make certain that none returned. I think it most probable 

 that owing to the darkness they do not return until the break of 

 day, and further, that they remain on the 7ving all night. This 

 last feat, though sufficiently startling, will, I am convinced, not 

 be deemed impossible by those who have had good opportuni- 

 ties (and made use of them) for studying the ways of swifts and 

 their wonderful powers of flight. As far as my observation goes, 

 the swift settles nowhere except at its own nesting-place. 



I shall be very glad of any information tending to throw light 

 upon the question, and I shall be very pleased to give any of 

 your correspondents any further information within my know- 

 ledge concerning this curious habit of the swifts, and the proofs 

 thereof, to set out which in this letter would take up too much of 

 your valuable space. 



White also says (p. 180, original edition) he has never seen the 

 swift carrying materials to its nest, and suggests that it usurps 

 that of the sparrow. This does not accord with my own ob- 

 servation here. I have repeatedly seen swifts taking bents of 

 grass in their beaks to their nests, and I have again and again 

 scattered feathers on the wind from the sound-holes in the 

 steeple, and from the steps of the cross in the churchyard, and 

 seen them eagerly seized within a few feet of my head by 

 numerous swifts. Their nests are neat, small, and shallow, and 

 very firm, the materials being glued together by the viscous 

 saliva of the builders. Aubrey Edwards. 



The Vicarage, Orleton R.S.O., Herefordshire, 

 October 13. 



Hughes's Induction Balance. 



Having just made a Hughes's induction balance, I have, in 

 the course of some experiments with it, observed what was new 

 to me, for I have not seen it mentioned in any account of the 

 balance. I take the liberty, therefore, of asking through your 

 columns whether the explanation resolves itself into the difference 

 between paramagnetic and diamagnetic substances. The aper- 

 tures of my bobbins are li inch in diameter ; my primary current 

 is from three Daniell's, and the break is a bent steel spring whose 

 free point just grazes the surface of a mercury cup, so that the 

 merest touch with a finger causes a series of regular breaks. 

 Now, if I place an iron or steel disk, or ring, such as a key-ring, 

 inside the aperture, the telephone sounds loudly if the plane of 

 the disk or ring is at right angles to the plane of the coils ; but 

 very very faintly if it is parallel to the plane of the coils. On 

 the other hand, if a disk, or ring, or coil of wire, of any of the 

 diamagnetic metals — copper, brass, zinc, silver, gold, aluminium, 

 lead — be used, the telephone sounds loudly if the plane of the 

 disk or ring he parallel to the plane of the coils ; but very faintly, 

 if at all, when it is perpendicular to the plane of the coils. 

 Further, if a short bar of soft iron, or of nickel, be inserted so 

 that the length of the bar is parallel to the plane of the coils, 

 almost no sound is heard ; but if it be turned through a right 

 angle so as to be perpendicular to the plane of the coils, the 

 sound is a maximum. Have we in this simple instrument the 

 ready means of distinguishing paramagnetic from diamagnetic 

 substances? J- Cook. 



Central College, Bangalore, S. India, September 26. 



