66 



NATURE 



\_May 19, 1 88 1 



hemisphere, it being understood that telegrams have been sent to 

 the Cape and to Australia (by Lord Crawford) with this object. 

 According to the above orbit, on july 9 the comet will have one- 

 fiflhof the intensity of light on the night of discovery. There is 

 no close resemblance of elements to those of any comet previously 

 calculated. 



The " Astronomische Nachrichten." — It is announced 

 that after the termination of the current volune, by authority of 

 the Prussian Government a new arrangement for the manage- 

 ment of this journal will take effect. It will be edited by Prof. 

 A. Krueger, the director of the Observatory at Kiel, in coopera- 

 tion with the president of the "Astronomische Gesellschaft," of 

 which association it will become a recognised organ. 



BIOLOGICAL NOTES 



LiMULUS POLYPHEMUS. — A paper on the anatomy, histology, 

 and embryology of Limulus polyphemus, by A. S. Packard, 

 jun., M.D. [Anniversary Mem. Boston Soc. Nat. Hist. 18S0), 

 may be regarded as a continuation of the author's former series 

 on the development and affinities of the king-crab. He discusses 

 fully the question of the affinities of that puzzling animal, 

 and combating the position of those zoologists who connect 

 Limului with the Arachnida, he sums U]i the facts which point 

 to the crustacean nature of Limulus as follows : — (l) The nature 

 of the branchiae those of Limulus being developed in numerous 

 plates overlapping each ether on the second abdominal limbs 

 (those of the Eutrypterida being, according to H. Woodward, 

 attached side by side like the teeth of a rake), while the mode 

 of respiration is truly crustacean ; (2) the resemblance of the 

 cephalothorax of Limulus to that of Apus ; (3) the general 

 resemblance of the gnathopods to tlie feet of Nauplius or larva 

 of the cirrhipedia and copepoda ; (4) the digestive tract is homo- 

 logous throughout with that of Crustacea, particularly the Deca- 

 poda, there being no urinary tubes as in Tracheata ; (5) ihe 

 heart is on the crustacean type as much as on the tracheate type, 

 and the internal reproductive organs (ovaries and testes) open 

 externally, at the base of and in the limbs, much as in Crustacea. 

 The paper is illustrated by seven plates showing the circulation of 

 Limulus, sections of the adult and of embryos, and details of the 

 structure of the eyes with comparison of these with those of Trilo- 

 bites, with which group the author, as in his first memoir, allies 

 the Merostomata. 



The Nummulitic Echinids of Egypt. — A monograph of 

 the Echinids contained in the Nummulitic strata of Egypt, by 

 M. P. de Loriol, is published in the Mem. ,Soc. Phys. et d'Hist. 

 Nat. de Geneve (torn, xxvii. 1S80, \"'^ p''.). The specimens 

 described by M. de Loriol were obtained mostly near Cairo and 

 Thebes. The fauna of the Nummulitic strata of Egypt has been 

 found by him as far as yet explored to contain forty-two species 

 of Echinids, or about the same number as that of the Nummulitic 

 strata of India ; that of the Canton of Schwytz has only thirty- 

 four, the Eocene f.auna of the Antilles only eighteen ; but the 

 Eocene fauna of the Pyrenees has as many as ninety-three. In 

 the present memoir, which is illustrated by ten plates, tv\'enty 

 new species are described. The author does not concur in Prof. 

 Jeffrey Bell's reasons for the formation of his new genus Paleo 

 lampas, considering that there are not sufficient grounds for 

 separating it from Echinolampas. Only four of the forty-two 

 species composing the Egyptian Nummulitic fauna are regular 

 Echinids, all the rest are irregular. Of the whole number all 

 but eight are peculiar to Egypt. Of the eight exceptions four 

 occur in the lower part of the Nummulitic formation at San 

 Giovanni Harione, in the Vicentin, three in that of the Pyrenees, 

 whilst the remaining one, Hcinispatangus depressus, has been 

 found in the Crimea in the sime beds as Echinolampas sub- 

 cylindrieus, which also occurs at San Giovanni Harione. 



Sponges of Lake Baikal. — In a recent note to the St. 

 Petersburg Academy, Dr. Dybowski says sponges occur in Lake 

 Baikal wherever the bottom is rocky or large blocks of stone or 

 wood are lying about. Close to the border of the lake, at a 

 depth of 2 to 6 metres, they have a sod or cushion-like form, 

 clinging to the stones, blocks, and (more largely) to decaying 

 wood. In a depth of 6 to 25 metres they become tree- or shrub- 

 like, with a height rarely exceeding 60 ctm. ; while from 25 to 

 100 m. depth the sod or cushion-like form recurs, and only thit 

 is met with. The colour of the sponges is generally more or 

 less dark grass-gi'een, somniaies olive-green or brown. But 



those got from depths of 60 to loo m., or found under stones, 

 are nearly quite while. 



Microscopical E.xamination of Farina. — In examining 

 any given kind of farina with the microscope to find whether a 

 less nutritive farina has been mixed w ith it, it has been common 

 to confine attention to the starch gran lies (which one may easily 

 be mistaken about) : Dr. Cattaneo holds (Re. hi. l.omb. Rend. 

 vol. xiv. fasc. v.) that greater importance should be attached to 

 the character of the bran-particles, some of which are never 

 wanting even in the most carefuUy-b ilted flour. These (as he 

 shows) differ in a marked way according to species. 



The Hypophysis in Ascidians. — While the hypophysis, or 

 pituitary gland, found in the cranial cavity of adult vertebrates 

 seems to be a rudimentary body without function, it is, in its 

 earlier development, furnished, like all active glands, with an 

 excretory passage into the alimentary canal. On the instance of 

 M. van Beneden, M. Julin has lately studied an enigmatical 

 organ in ascidians, a glandular apparatus under the brain (dis- 

 covered by Hankow), which, it was thought, might be homolo- 

 gous with the pituitary gland of vertebrates. M. Julin examined 

 the gland, the so-called anterior tubercle or vibralile organ, and 

 various connected organs, in four species of ascidians at Leewik, 

 on the Norwegian coast, and his researches (lately described to 

 the Bel;jian Academy) appear to confirm M. van Beneden's 

 conjecture. M. Julin is unable to regard the vibratile organ as 

 an olfactory organ (the ordinary view) ; it receives no nerve- 

 branch, and no olfactory cells can be found in its vibratile 

 cylindrical epithelium. It is (he considers) merely the enlarged 

 mouth of the excretory canal of the gland below the brain, 

 leading into the buccal region, while the gland itself represents, 

 in permanent state and functional activity, the embryonic 

 hypophysis which becomes rudimentary in vertebrates. The 

 rSle of the gland remains in obscurity. (Anatomical details 

 will be found in the Academy's Bulletin, No. 2) 



PHYSICAL NOTES 



An extremely ingenious explanation of the peculiar green 

 phosphorescence observed by Crookes in his researches on high 

 vacua has recently been given by Mr. J. J. Thomson of Cam- 

 bridge. This phos]ihorescence appears on the inner surfaces of 

 the exhausted glass tubes whenever they are exposed to the so- 

 called molecular bombardment of particles projected from the 

 negative electrode. Mr. Thomson points out firstly that, as 

 predicted by Clerk-Maxwell and verified by Rowland, a moving 

 electrified particle acts as a current of electricity and possesses 

 an (electro-magnetic) vector-potential. Now where such an 

 electrified particle strikes a glass surface and rebounds, its 

 change of velocity is accompanied by a change of vector- 

 potential, and the glass against which it impinges and rebounds 

 will be subjected to a rapid change in electromotive force. But by 

 Clerk-Maxwell's electro-magnetic theory of light this is precisely 

 v\hat happens when a ray of light falls upon it. And therefore 

 it phosphoresces as it would under the impact of an actual ray 

 of light. It would be interesting to inquire whether all jihosphor- 

 escent and fluorescent phenomena are capable of an analogous 

 explanation in accordance with Clerk-Maxwell's theory. 



Mr. E. H. Cook proposes (Phil. Mag.) the term sonorescence 

 as suitable to apply to the phenomena discovered by Graham 

 Bell and investigated by Mercadier, Tyndall, and others, of the 

 direct conversion of intermittent radiations into sound. The 

 new name is obviously sugge4ed by analogy with fluorescence 

 and calorescence, but does not seem quite a happy one. Stokes 

 gave the name of fluorescence to the phenomenon of the change 

 of non-luminous ultra-violet rays into luminous ones. Akin 

 gave the name of calcescence to the phenomenon of the change of 

 non-luminous heat-rays into luminous ones (as in the lime-light), 

 but the term has been superseded by Tyndall's term calorescence, 

 which is etymologically unfortunate, seeing that the Latin verb 

 is calesco, not caloresco. By strict analogy the term sonorescence 

 should mean the conversion of sound into luminous rays, not the 

 reverse change, to which Mr. Cook applies it. 



The researches of Edlund, Joubert, and others have left no doubt 

 that the voltaic arc possesses an electromotive force of its own 

 acting in a direction opposite to that of the current which 

 sustains the arc. The principal work of maintaining the arc 

 appears indeed to be spent in overco 1 ing this opposing force, 

 and is not occasioned by the resistance of the arc itself, which is 

 small. M. Alfred Niaudet has lately announced the observation 



