Oct. iS, 1 888] 



NATURE 



589 



the limbs. Of these nails the fourth is 15 mm. long and of a 

 uniform width of 4 mm., ending very bluntly ; the fifth is very 

 slightly shorter than the fourth, broad at the base (8 mm.), 

 tapering rapidly to a blunt point, the two together forming an 

 outline rather like that of a goose-mussel (Lepas). The nails of 

 the third, second, and first digits, very much smaller, form a 

 series gradually diminishing in size in the order named, and con- 

 stitute a second row on the inside of the fourth and fifth, by 

 which, as stated, they are completely concealed from view. 

 What corresponds to the palm is the cleft between the two rows 

 of digits. 



The hind-limbs are also short, with the soles turned outwards. 

 What appears to be the fifth (anterior) digit is very short, with a 

 short, broad, and strong nail ; the fourth is armed with a long 

 (7 mm.) narrow, curved, and sharp claw, while the claws of the 

 third, second, and first are broad, flat, rounded at their points, 

 and joined together by a membrane which extends nearly to 

 their points. On the sole there is a hard, elongated, horny 

 tubercle crossing it transversely. 



The tail, 2 cm. long, and 5 mm. wide at the insertion, tapers 

 to 3mm., and terminates in a knob-like tip. 



About 15 mm. in front of the vent (? cloaca) there is a pouch 

 in the integument about 4 mm. wide, with the opening directed 

 backwards and having a depth in a forward direction of from 

 4-5 mm. The surface of this pouch is devoid of hair, but 

 the bare area is surrounded by thick fawn-coloured fur, with a 

 slightly reddish tint ; it is possible, however, that this reddish 

 tint is due wholly or in part to some ferruginous-looking sand 

 which is much mixed up with the fur. The body generally, 

 with the exception of the lower two-thirds of the tail, which is 

 bare, is covered with fur of a rather lighter tint. 



With regard to the internal parts, it is unfortunate that the 

 specimen came to us completely eviscerated, and in a bad state 

 of preservation generally ; but in a small part of the lower 

 bowel which was left, remains of ants were found. The bowel 

 terminates at a wide vent (? cloaca), and I can find no trace of a 

 separate genital aperture, nor of such openings into the supposed 

 cloaca. 



I have hot yet had time to examine with minuteness the 

 skeleton, which unfortunately is also considerably damaged, 

 especially about the occipital region ; but from a cursory examina- 

 tion of the recently-skinned body, I can note the following 

 points, with, I believe, accuracy^: — 



Cranium relatively large ; no bony orbits ; zygomatic arches 

 present ; well-developed shoulder-girdles with slender clavicles ; 

 pectoral muscles large ; pelvis large and strong, with a rather 

 wide symphysis pubis, but no epipubic bones, either actual or 

 rudimentary ; ribs, 14 ; angle of lower jaw markedly inflected. 

 The teeth are peculiar, and require a more extended 

 description than I can give at present, but the formula appears 

 to he — 



ilc I, m 6 h t*LH 

 31 5V / i, m 



This, however, may require some modification, as just posterior 

 and external to the premolar (or first molar) of the right ramus 

 of the mandible there is a small rudimentary conical tooth, 

 which is not to be found on the opposite side, nor at 

 corresponding positions in the maxilla. 



I do not pretend to be a zoological expert, but 1 cannot help 

 being struck with the resemblance both of the lower jaw and of 

 the general characters of the teeth to the pictures of the jaws of 

 Amphitherium as figured in various osteological works. I am 

 now endeavouring to obtain other specimens, .and meanwhile am 

 having careful drawings made of the various parts of the present 

 example of what appears to be a remarkably curious and inter- 

 esting animal even in this land of strange and antique types. 



E. C. Stirling. 



The University, Adelaide, South Australia, August 29. 



Nomenclature of Determinants. 



Nature of October 4 opens with a review of a book on 

 "Determinants" by two pupils of Prof. Valentin Balbin, 

 whose energy and enthusiasm have done so much for mathe- 

 matics in the University of Buenos Ayres. In regard to the 

 naming of the various special forms of determinants, your re- 

 viewer says : — " The nomenclature adopted in the second book 

 differs in some particulars from that employed by Muir. Thus, 

 our authors do not follow him in substituting ' adjugate ' for the 



4 



4/ 



more euphonious and more familiar adjective ' reciprocal,' and 

 they agree with Scott and others in calling those determinants 

 ' orthosymmetricil ' which Muir names 'persymmetric.' We 

 think that their name ' determinante heniisiinrtrica ' is a 

 distinct improvement on the old ' zero-axial skew determinant,' 

 but ..." 



Now, as I have gone on a definite principle in the selection 

 of the technical terms used in my book, and as I believe that 

 this principle is one which receives very general approval among 

 students of science, I shall be glad if you will allow me to direct 

 attention to it. It is that, unless very strong reasons to the 

 contrary can be adduced, the first name given to a scientific 

 object or concept should not be departed from. 1 In more 

 aphoristic form, the multiplication of synonyms is a great evil. 

 Judged by this principle, the terms " adjugate," " persymmetric," 

 and "skew " deserve the place I have given them. " Adjugate," 

 as applied to a determinant, was a generation old before 

 "reciprocal" was proposed; and — what is no mean additional 

 recommendation — it carries with it the sanction of the highly- 

 honoured names of Gauss and Cauchy. To outweigh these 

 claims there is very little to be said for the rival word. It is 

 not more appropriate ; indeed, the kind of connection to be 

 indicated does not involve the idea of reciprocity at all. It is 

 true, as your reviewer says, that "reciprocal " is a more familiar 

 word ; but the use of a familiar word in a new and therefore 

 unfamiliar sense is surely not to be commended. In regard to 

 " persymmetric," similar language may be employed. It was 

 proposed by Sylvester, and was in use for years by him and 

 others before " otthosymmetric " made its appearance. The 

 latter is not an etymological mongrel, but it is also not one 

 whit more appropriate than the word it seeks to supplant, and 

 it is the unfortunate parent of the monster " doppelt-orthosym- 

 metrisch." It never was heard in England until 1880, and I 

 regret that my friend Mr. Scott should have seen cause to in- 

 troduce it. As for the third word, "skew," the arguments in 

 its favour are still stronger. The determinant in question was 

 called "skew" in English and "gauche" in French, by Cayley, 

 ai far back as 1846; and these words, and their German and 

 Italian equivalents, are to be found employed in scores of 

 original memoirs by the highest mathematicians. " Hemisym- 

 metric" is but of yesterday, and, so far as I know, has never 

 been used by any mathematician of note. 



Is it merely a proof of the decadence of our insularity to find 

 a welcome given by Englishmen to terms of foreign coinage 

 which have been wantonly proposed to displace the original 

 words. of Cayley and Sylvester? and what does it prove to find 

 Germans, who at first derided the tropical luxuriance of Syl- 

 vester's nomenclature, now out-Heroding Herod without having 

 Sylvester's exculpating accompaniment of tropical luxuriance of 

 ideas ? 



Your reviewer's protest against Dostor's introduction of "mul- 

 tiple determinants " I cordially support, and only wish that he 

 had taken space to show the numerous absurdities connected 

 therewith. Thomas Muir. 



Beechcroft, Both well, N.B. 



A Shadow and a Halo. 



" E. W. F." may see the phenomenon he describes any sunshiny 

 morning or bright moonlight night, when the dew is heavy on 

 the grass. The halo being caused by reflection at a small angle 

 of the sun or moonlight from the wet surfaces of the blades of 

 grass, enhanced by contrast with the dark shadow (and having 

 nothing to do with moist air), its brightness would no doubt be 

 increased by the foreshortening and consequent apparent com- 

 pression of the reflecting surfaces on the slope. The neighbour- 

 hood of a high hedge would diminish it by lessening radiation, 

 and the consequent cooling of the grass and deposition of dew 

 upon it. 



Nature naturally takes no account of moral analogies, of 

 which Nature herself is full. Else one might note that a man 

 never sees a halo round his own head unless he tuins his back 

 to the light. B. W. S. 



Hampstead Heath, October 6. 



Often and often in walking or riding over the chalk downs 

 of Wiltshire or Hertfordshire I have observed a bright halo 

 surrounding the shadow of my head. This is usually cast by sun 



1 The introduction of " cominuant " may seem to do violence to this 

 principle ; but the letter referred to by ; o.ir revitwer will shew the opposite. 



