Oct. 27, 1887] 



NATURE 



609 



rise to individuals of the fourth generation, and the germ- 

 cells of these last individuals mast contain eight different 

 ancestral plasmas ; similarly the germ-cells of the fifth 

 generation must contain sixteen ancestral plasmas, and 

 so on. It is thus clear that in a very small number of 

 generations the composition of the germ-plasma must 

 become extremely complicated : by the tenth generation 

 it would already contain 1024 different ancestral plasmas. 



We do not know how far this may go, because we do 

 not know how small are the primary elements of germ- 

 jlasma, nor do we know how many of these elements 

 lay be indispensable for the youngest and smallest germ- 

 cells. But if we imagine these elements to be excessively 

 small, this process of doubling the number of ancestral 

 jlasmas in each generation must have come to an end 

 iifter a certain number of generations, whether they were 

 io, 20, 100, or 1000 ! 



From the time at which the germ-plasma first attained 

 Jts utmost complexity further sexual propagation was only 

 possible by halving the number of ancestral plasms con- 

 lined in the germ-plasma. Clearly, this process of 

 living ought to take place in male germ-cells as well as 



female ones, but at this moment we are only sure of 

 b existence in the latter. We have seen that one-half of 

 le germ-plasma contained in the nucleus of the egg-cell 



expelled in the second polar cell. That the nuclear 

 lubstance thus expelled is true germ-plasma, is not a 

 lere supposition, but a certainty. We know of develop- 

 fing eggs which are either fertilized or unfertilized, and in 

 'the latter case they develop by parthenogenesis. Such are 

 the eggs of the honey-bee. We may assume that if these 

 eggs remain unfertilized they will expel only one polar 

 globule, but that if, on the other hand, they are penetrated 

 by a spermatozoon they will also expel the second 

 globule. Thus the same idioplasma that is expelled 

 from the fertilized Qg'^ remains, and forms half of the 

 first segmentation-nucleus in the parthenogenetic t.'gg. 

 It must therefore be true germ-plasma. 



I do not doubt that this is the true significance of the 

 formation of a second polar globule. We can see the 

 necessity on theoretical grounds for the removal of half 

 the number of ancestral germ-plasmas ; and we actually 

 find that half of the germ-plasma is removed in every 

 sexual tgg. 



If this reasoning be correct, our views on sexual propa- 

 gation must undergo a total change. Fertilization is no 

 longer an unknown impulse given to the egg-cell by the 

 entrance of a spermatozoon, but it is simply the union of 

 the germ-plasmas of two individuals. The spermatozoon 

 is no longer the spark which kindles the powder, or the 

 relatively small force which converts potential into actual 

 energy, but it is merely the carrier of germ-plasma of a 

 certain individual, possessing the necessary qualities for 

 reaching, penetrating, and fusing with the bearer of germ- 

 plasma from another individual. There are no essential, 

 but merely individual, differences between the nuclear 

 substance of the spermatozoon and that of the ovum. 

 There are no such things as male or female nuclear sub- 

 stances, but merely male and female cells, carriers of the 

 immortal germ-plasma. The differences are wholly indi- 

 vidual and of merely secondary importance, and nothing 

 corresponding to the ordinary notions implied by the 

 terms male and female exists in germ-plasma. 



If this be so, then it is clear that the fact of sexual 

 propagation demands a new explanation. We must 

 attempt to explain the reason why Nature has in- 

 sisted upon the rise and progress of sexual propagation. 

 If we bear in mind that in sexual propagation twice as 

 many individuals are required in order to produce any 

 number of descendants, and if we further remember the 

 important morphological differentiations which must take 

 place in order to render sexual propagation possible, we 

 are led to the conviction that sexual propagation must 

 confer immense benefits upon organic life. I believe that 



such beneficial results will be found in the fact that sexual 

 propagation may be regarded as a source of individual 

 variability, furnishing material for the operation of natural 

 selection. I believe that sexual propagation has become 

 prevalent among the higher organisms for the purpose of 

 conserving and multiplying that individual variability 

 which owes its first origin to the Protozoon condition of 

 such higher organisms. But it is not now my purpose to 

 speak further upon this subject : I have already discussed 

 it elsewhere (" Die Bedeutung der sexuellen Fortpfianzung 

 fiir die Selections-Theorie," Jena, 18S6). 



Whatever is to be said for the above hypotheses, the 

 facts I have the honour of bringing before you to-day seem 

 at least to prove that sexual propagation depends on the 

 removal of half of the germ-plasma of the t%<g and the 

 replacement of it by the same quantity of germ-plasma of 

 another individual. This is now a fact which may be 

 regarded as indisputable ; and, further, the existence of 

 true parthenogenesis is now proved beyond doubt. For 

 we know now that an egg which expels only one polar 

 globule enters without delay into embryonic development, 

 inasmuch as it has retained the whole of its germ- 

 plasma. 



THE TOTAL ECLIPSE OF LAST AUGUST IN 

 JAPAN. 



TTHE eclipse has come and gone, and our little party is 

 ■*■ on its way home with a few papers and a small box 

 of glass plates — a rather meagre showing for the hard 

 work of our summer months. Although we were so un- 

 fortunate as to have uninterrupted cloud throughout the 

 entire duration of the eclipse, our expedition to Japan has 

 not been so dismal a failure all told. Apart from sundry 

 observations of minor importance contributed by volun- 

 teer observers at scattering stations for whom I had pre- 

 pared instructions. Dr. W. J. Holland, who joined the 

 Expedition at my invitation as naturalist, has been actively 

 engaged in botanical and entomological research in fruit- 

 ful fields, and has a good harvest to report. He has also 

 valuable notes upon his ascent of Nantaisan, Asama- 

 yama, and Nasutake (which latter he appears to have 

 been the first foreigner to ascend) ; while the separate 

 expedition to the summit of Fuji-san (12,400 fest), which 

 I had the pleasure to carry out under the auspices of the 

 Boyden Fund of the Harvard College Observatory, and 

 on which I had the highly-valued co-operation of Dr. E. 

 Knipping, Meteorologist of the Japanese Weather Service, 

 resulted, among other things, in the determination of its 

 rare fitness as a site for astronomical observation — of 

 which more elsewhere. 



With reference to the preliminaries of the Eclipse Ex- 

 pedition it is necessary to state that early in the present 

 year the trustees of the Bache Fund of the National 

 Academy of Sciences, Washington, made a grant to Prof. 

 Newcomb, the Superintendent of the Nautical Almanac, 

 for observing the total solar eclipse of August 19, 1887. 

 Prof. Newcomb determined the general lines of research to 

 be undertaken, decided upon locating the observing- 

 station in Japan, and placed me in charge of the Expedi- 

 tion. After some weeks of preparation in Washington 

 and elsewhere, I set out for Japan on June 9, and arrived 

 in Yokohama a month later. There was no small diffi- 

 culty attending the definitive location of the instruments 

 for observing the eclipse, owing to the deficiency of precise 

 meteorological information regarding the region of the 

 shadow-path. All existing data were kindly placed at my 

 disposal by the officers of the Japanese Government, and 

 several of the departments contributed in other ways to 

 the assistance of an expedition which, had the skies been 

 favourable, could not have failed of entire success. 



Going northward from Tokio along the line of the 

 Japanese Railway Company, to the courtesy of whose 



