158 



NATURE 



[December 14, 1899 



October 8, 1894), Prof. Barnard decided to observe it as con- 

 tinuously as possible, to settle this question. Tisserand's results 

 indicated that the line of apsides of the satellite's orbit should 

 also have a motion of + 882° a year, or + 2° "42 daily, giving a 

 complete revolution in five months. From the Lick measures 

 he computed the semi major axis of the orbit to be 47"'9c6, the 

 eccentricity 0'oo73, and longitude of Perijove for 1892, Novem- 

 ber I, =-4°. Prof. Barnard's more recent measures enable 

 him to revise these values, and his results are contained in the 

 Asironomual Journal, No. 472. On calculating the position 

 of the satellite from Tisserand's value of the motion, a consider- 

 able error is found, and the daily motion of the apse line is 

 probably more nearly +2°'465 or 900° yearly, giving a complete 

 revolution of the orbit in 4*9 months. 



An interesting question that may also be settled by continued 

 observation of the satellite is the distribution of matter at the 

 equator of Jupiter itself, as the motion of the perijove of the 

 satellite does not agree with that deduced from the actual polar 

 compression of the planet. 



During the whole of the measures half the field of view was 

 covered with a piece of smoked mica, through which the bright 

 limb of the planet was observed, and the distances measured 

 from the limb afterwards reduced to the centre by previous 

 measures of the planet's diameter with the same instrument. The 

 increased number of elongations measured gives a much more 

 correct value of the period. The value now given is 



iih. 57m. 22-647S., 

 which Prof. Barnard considers correct to one-hundredth part of a 

 second. 



Partial Eclipse of the Moon, December 16— There 

 will be a partial eclipse of the moon, visible at Greenwich, during 

 the early morning of Sunday next, in respect to which the 

 following particulars apply : — 



First contact with penumbra = loh. 337m. ; with shadow = 

 lih. 44-6m. 



Second contact with penumbra = i6h. iS'lm. ; with shadow = 

 I5h. 1 7 •2m. 



Magnitude of eclipse (moon's diameter = i) = 0'995. 



First contact with shadow occurs at a point 66° from the 

 north point towards the east, measured along the moon's limb. 



Last contact with shadow at a point 59° from north point 

 towards the west. 



The eclipse is visible in Western Asia, throughout Europe 

 and Africa, and in Eastern America. 



OccuLTATiON OF Neptune, DECEMBER i6.— There will 

 be another occultation of Neptune during the early morning of 

 Sunday, while the moon is still in the penumbra of the earth's 

 shadow after the partial eclipse. The following are the 

 particulars for observers near London : — 



Greenwich Mean Time of "\ ,Q „ -,-. i_ ^j u 



conjunction in R.A....r^99 December i6d. I4h. 53m. 15s. 



Limits of latitude, 90° N. to 30° N. 



Neptune passes the meridian of Greenwich at I3h. 40m., so 

 that it will be well situated for observation of the occultation. 



Meridian of Universal Time. — In the Revue Scientijique, 

 Ser. 4, vol. 12, p. 526, M. C. Tondini di Quarenghi summarises 

 most of the evidence in favour of and against the adoption of 

 the meridian of Greenwich as the initial meridian for universal 

 time. The chief objection is cited as a physical one, viz., the 

 extreme uncertainty of the meteorological conditions, rendering 

 celestial observations impossible on a large proportion of the 

 days and nights throughout the year. The advantages of the 

 site at Jerusalem suggested by the Italian Government are the 

 superior observing conditions and the possibility of the district 

 being declared neutral ground, thus ensuring the permanence of 

 the station irrespective of political changes. A further advan- 

 tage would be the possibility of e.-^tablishing other subsi- 

 diary stations at intervals along the meridian, 



NO. 1572, VOL. 61] 



THE DEVELOPMENT OF GANGLION-CELLS 



AND NERVES} 

 "T^HE results of this memoir largely are in keeping with 

 -*■ certain revolutionary changes in embryological "doctrine, 

 with which the names of Klaatsch, Miss Julia Piatt, Gorono- 

 witsch and others are identified. According to their views 

 certain vertebrate structures, which have hitherto been 

 genetically referred wholly or in part to the mesoderm, such as 

 scales, certain cartilages, and even bones, are in fact directly 

 or indirectly products of the outer layer of the embryo, the 

 ectoderm or epiblast. This is only a brief and very general 

 -Statement of the tendency of their lines of research, and it 

 may be added that as to the details there exist important 

 differences between the different observers. It will not be 

 needful to review all their conclusions here. Our concern is 

 solely with the aspect of the question presented to us by Dr. 

 Goronowitsch in his memoir. 



Researches on the development of nerves and ganglia date 

 back to Remak, whose conclusions as to their mesoblastic origin 

 from the protovertebrce or mesoblastic somites were commonly 

 held as recently as twenty-five years ago. About then date the 

 researches of Balfour and Marshall, who maintained that these 

 structures arose as outgrowths of the central nervous system, 

 and that therefore they were epiblastic in origin. 



Later on their conclusions were somewhat modified by Beard^ 

 in the discovery that the posterior root-ganglia, both cranial and 

 spinal, did not develop as actual outgrowths from the central 

 organ, but that their foundations were to be traced to the deeper 

 portions of the epiblast outside the limits of the future brain and 

 spinal cord. It was also demonstrated that the cranial ganglia 

 received additions from special regions of sensory epiblast, since 

 termed by Kupf^er "placodes," on the level of the notochord 

 and above the gill-clefts. Thus, for the sensory portion of each 

 cranial ganglion, two sources of origin could be identified, and 

 the parts so derived were termed neural and lateral respectively. 

 A few years ago Kupfifer added a third source, and described an 

 " epibranchial " ganglionic foundation as arising from it. 

 Kupffer's results were obtained in the lamprey, unquestionably 

 one of the most difficult forms among vertebrate animals for the 

 study of organogeny. His results have never been confirmed 

 by any other observer, either in the lamprey or in any other 

 vertebrate. 



Whilst it is certain that his epibranchial ganglia have no 

 existence in Elasmobranch fishes, it is also in embryos of these 

 easily demonstrated how Kupffer fell into the error of siipposing 

 their presence. In fine, had his researches been carried to 

 sufficiently early "stages" or phases he would have seen thai! 

 his lateral and epibranchial ganglia merge into one, the found- 

 ation of a lateral ganglion. 



Since Kupffer's researches were fully published in 1S94-5,, 

 embryological investigation of the development of cranial and 

 .spinal nerves and ganglia has been put somewhat in the shade 

 by brilliant researches into their comparative anatomy at the 

 hands of Allis, Dixon, Ewart, Fiirbringer, Haller, Strong and 

 F. J. Cole. Pages and pages might be filled in review of these, 

 along with a critical digest of numerous- other papers, embryo- 

 logical and morphological, issued since 1885. Controversies 

 have been waged as to the morphological nature of certain 

 nerves and ganglia, as to their mode or modes of development, 

 and as to the way — apparently a simple problem, but by no 

 means such — in which nerve- fibres arise. 



The work under review is only in a minor degree a contri- 

 bution to a knowledge of the morphological nature of nerves, 

 i.e. in so far as it relates to the olfactory and auditory nerves. 

 On the other hand, it emphatically claims to furnish decisive 

 replies to the two latter questions, as to the mode or modes of 

 development of ganglia and of nerve-fibres. If the conclusions 

 drawn by Goronowitsch from his researches can be upheld, it 

 would seem to follow that the investigations of the past 

 twenty-five years — except those of Sedgwick — have been largely 

 in vain. 



According to Dr. Goronowitsch, what Balfour and Marshall 

 regarded as outgrowths of the central nervous system, and 

 termed " the neural ridges," have nothing to do with the 

 development of the cranial ganglia. The existence of these 

 " ridges " of cells he does not dispute, but he maintains that 

 the component cells become resolved into the surrounding meso- 



1 Unteisuchungen iiber die erste Anlage der Kranialnerven bei Salnto 

 fario." By N. Goronowitsch. Nouveaux M^moires de la Soci6t6 impdriale 

 des Naturalistes de Moscou, T. xvi. L. i, pp. 1-55, 3 plates. 



