364 



NATURE 



\An07tst 30, 1877 



rediscovery, which have been prepared by Herr Mahn on 

 his suggestion. They appear in the Viertcljahrsschrift 

 dcr astronomischen Ccsellscliaft, 12 Jahrgang, 2 Heft. 

 Encke's period, 707 years, would bring the comet to 

 perihelion again in 18S3, but Mr. W. E. Hummer, now of 

 the University Observatory at Oxford, some years since 

 stated that a period of 69'2 years would better agree with 

 normal places which he had very carefully prepared. The 

 comet may therefore visit us in 1881, or possibly much 

 earlier with the unknown effect of perturbation. The 

 sweeping-ephemerides are arranged upon a plan con- 

 veniently indicating the line in which the comet should be 

 sought at a particular date. It is a case where the 

 "orbit-sweeper," suggested by Sir George Airy, and 

 advocated by Prof. Winnecke, would, if provided with an 

 object-glass of sufficient optical capacity, render much 

 assistance. 



The Companion of Sirius. — In the Comptcs Rendus 

 of the French Acadeniy of Sciences, August 13, M. 

 Flammarion has a graphical representation of the orbit 

 assigned by Dr. Auwers, to the perturbing companion of 

 Sirius and of the observed course of the small star dis- 

 covered by Mr. Alvan Clark, with the view to illustrate 

 the increasing differences between theory and observa- 

 tion. Allusion was made to this subject in Nature 

 (vol. xiii. p. 428), where the differences of Dr. Auwer's 

 ephemeris, 1872-75, were given. The latest measures of 

 the Clark-companion at Washington, show for lS77'2i, 

 position {c — 0), -\- 6°-g, distance — o"'88. 



Prof. Asaph Hall found no other star in the vicinity of 

 Sirius nearer than one of the thirteenth magnitude, which 

 was measured on February 28, 1877; position II4^'9, 

 distance 72"'09 ; probably the star seen by Mr. Marth at 

 Malta in January, 1865. An examination of the vicinity 

 with the great refractor was made at the request of M. 

 Tempel, of Florence, who had suspected the existence of 

 several small stars near Sirius. 



Satellite of Mars.— One of the newly-discovered 

 satellites of Mars was observed by M. M. Henry at the 

 Observatory of Paris, on August 27. 



At I2h. 9m. mean time, position 249° 56', distance 

 85"'2, the satellite was very faint, and only observable 

 when the planet was screened from view. 



BIOLOGICAL NOTES 



The Development of the Nerves in Verte- 

 brates. — Mr. Balfour's discovery that the spinal nerves 

 of sharks and rays are developed as outgrowths from the 

 central nervous system has been followed by a similar 

 revelation with regard to birds. Mr. (now Dr.) A. M. 

 Marshall (of Cambridge) has given an account of investi- 

 gations respecting the origin of nerves in the fowl {Journ. 

 yj«rt/., April, 1877), describing a longitudinal ridge arising 

 on the summit of the neural canal, and giving off paired 

 processes, the rudiments of the posterior roots of the 

 spinal nerves. Hensen has made analogous observations 

 on the spinal nerves of the rabbit. The anterior roots 

 arise later, distinct from one another, as processes from 

 the spinal cord. Mr. Balfour has endeavoured to solve 

 the difficult question of the relations of the cranial to 

 spinal nerves. He finds as yet no traces in the brain of 

 anything comparable to anterior roots of nerves ; all the 

 nerves are posterior roots. The fifth, or trigeminal, 

 arises from the dorsal summit of the hind-brain very 

 early, just like a dorsal root of a spinal nerve. This nerve 

 also, instead of being a compound one, is at any rate in 

 its origin perfectly simple. The auditory nerve and the 

 facial arise by one common root. The glossopharyngeal 

 and vagus have a series of distinct roots. In an adult 

 Scyllium twelve separate strands have been counted in 

 the vagus nerve. This number, and their origin like so 

 niany separate spinal nerves, opens up interesting questions 

 in regard to the primitive segmentation of the head and 



the loss or condensation of segments in the evolution of 

 the vertebrates. Dr. Marshall's observations on the 

 cranial nerves of the chick, so far as they go, correspond 

 to Mr. Balfour's. It appears that there is no definite 

 indicalion of a limit between head and trunk afforded by 

 the central nervous cord, by the outgrowths from it, or by 

 the mode of development of the nerves. It is open for 

 consideration whether the absence of anterior roots to 

 the cranial nerves may not furnish such a limit ; this 

 would be very convenient for morphology. 



Insect Aid in Fertilisation of Flowers.— Mr. 

 Thomas Meehan, of Philadelphia, continues to bring 

 forward cases to show that many flowers are not so 

 dependent on insect fertilisation as has been imagined. 

 Recently {Proc. Acad. Nat. Sciences, Philadelphia, 1877, 

 p. 128) he has instanced the common mignonette, which 

 usually does not seed when forced in greenhouses in 

 winter. It has been asserted that this is due to the 

 absence of suitable insects to produce fertilisation. But 

 last winter I\Ir. Meehan's specimens took to producing 

 seed in abundance, two to six perfect seeds in every 

 capsule. This showed that some other circumstance had 

 come into play which affected the reproductive organs, 

 insect aid having been as much absent as in other cases. 



Insectivorous Plants. — Dr. C. Cramer, of Zijrich, 

 publishes, under the title " Ueber die Insectenfressenden 

 Pflanzen," a useful epitome of all that has at present been 

 recorded respecting the singular phenomenon of "Insecti- 

 vorous Plants." In a series of papers in Flora, on 

 the Mechanics of the Movements of these plants, A. 

 Batalin calls attention to a hitherto neglected paper of 

 Oudema'ns, published (in Dutch) in 1S59, in which he 

 describes the greater part of the phenomena of irritation 

 in Venus's fly-trap {Dioiuva muscipula), agreeing in 

 almost every point with the description subsequently 

 given by Darwin and others. 



Spontaneous Movements in Plants. — M. E. 

 Rodier, of Bordeaux, has described a singular scries of 

 automatic or spontaneous movements in a well-known 

 water-plant, CeratopJiylluin dcmersum. They consist of a 

 rhythmical motion caused by a curvature of the axis 

 extending over six hour;, which is neutralised in tlie 

 course of the next twelve hours, and followed by a cur- 

 vature in the opposite direction extending over four hours, 

 which is again neutralised in four hours, the whole cycle 

 thus extending over a period of twenty-six hours. The 

 movement appears to be entirely unaffected by light. 



DISCOVERY OF OXYGEN IN THE SUN BY 

 PHOTOGRAPHY, AND A NEW THEORY OF 

 THE SOLAR SPECTRUM'' 



I PROPOSE in this preliminary paper to indicate the 

 means by which I have discovered oxygen and 

 probably nitrogen in the sun, and also to present a new 

 view of the constitution of the solar spectrum. 



Oxygen discloses itself by bright lines or bands in the 

 solar spectrum and does not give dark absorption lines 

 like the metals. We must therefore change our theory of 

 the solar spectrum, and no longer regard it merely as a 

 continuous spectrum with certain rays absorbed by a 

 layer of ignited metallic vapours, but as having also bright 

 lines and bands superposed on the background of con- 

 tinuous spectrum. Such a conception not only opens the 

 way to the discovery of others of the non-metals, sulphur, 

 phosphorus, selenium, chlorine, bromine, iodine, fluorine, 

 carbon. Sic, but also may account for some of the 

 so-called dark lines, by regarding them as intervals 

 between bright lines. 



It must be distinctly understood that in speaking of the 

 solar spectrum here, I do not mean the spectrum of any 



' Paper by Prof. Henry Dr.iper, M.D. Read before the American Philo- 

 sophical Society, July 20, 1877 We are illdebted to Dr. Draper's kindness 

 for the plate and illustrations which accompany this pjper. 



