16 



THE AMEKICAN MONTHLY 



[January, 



them it was seen that only one of them 

 was filled with protoplasm ; the other, 

 on the contraiy, was entirely empty. 

 I was able to observe, from certain 

 peculiarities, that the shell before dis- 

 tinguished as the clearer was now the 

 empty one. In the isolated plasma 

 of the darker colored shell I found 

 two entire, and one disintegrated nu- 

 cleus. The two entire nuclei revealed 

 a large number of smaller, darker-col- 

 oi-ed bodies in a less deeply colored 

 ground-substance, and surrounding 

 them was distinguished an evident 

 double contoured uncolored nucleus- 

 membrane. Among the remains of 

 the third nucleus could be distinguish- 

 ed, more or less clearly, within the 

 less deeply colored general mass, a 

 darker colored central body. 



I have alluded to the process de- 

 scribed as copulation, although I have 

 not observed the union of originally 

 separated individuals. Since in no 

 case can we regard it as a division, it 

 may onl}- be said against my assump- 

 tion that it might be a process ol' re- 

 juvenation, in which one animal has 

 constructed a new dwelling around its 

 protoplasm, and forsaken its old one. 

 I believe this objection is disposed of 

 by the observation of the active pseu- 

 dopodal action at the beginning of the 

 process, by the destruction of the one 

 nucleus, and also by the fact that not 

 the clear but the darker shell, at the 

 end of the whole process, contained 

 the plasma-body. All this does not 

 accord with the appearances observed 

 in rejuvenation. I will not neglect to 

 add, that a large number of difflugia, 

 of the same species, which were found 

 in the same watch-glass, after careful 

 observation, all showed only one or 

 two nuclei, each nucleus with a sin- 

 gle large nucleolus. 



If I am not, then, at fault in con- 

 sidering the observed process as cop- 

 ulation, the following facts result: — 



I. Copulation takes place among 

 rhizopods as among infusoria. 



3. As among infusoria, during cop- 

 ulation there also occurs a stage of low 

 vital energy. 



3. In course of the processes a de- 

 struction of the cell-nucleus takes 

 place. 



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Vol. V (1884), Nos. 2-12, yi.oo. 



Microscopic Meteorites, — 



There are constantly floating in the air, 

 and falling to the earth from space, mi- 

 nute particles of impalpable dust. On 

 the snow-clad summits of mountains, 

 on the ice and snow of the polar re- 

 gions, and at the bottom of the sea, 

 these particles slowly accumulate, and 

 occasionally they are collected and 

 studied mici'oscopically and chemi- 

 cally. While some of this dust may 

 readily be recognized as of terrestrial 

 origin, much of it is undoubtedly of 

 a meteoric character — cosmic dust, 

 unlike anything else known upon 

 the earth. An alloy of nickel, co- 

 balt and iron is not known to occur 

 anywhere upon the earth, but me- 

 tallic spherules containingthese metals 

 were found on the ice-fields of Green- 

 land, and spherules of iron have 

 also been found in the abyssal depths 

 of the ocean, which are supposed 

 to have the same origin. Perhaps 

 they are from the luminous trains of 

 meteorites or shooting-stars, which, 

 losing their incandescence, sink as 

 impalpable dust upon the polar snows, 

 or into the still ocean depths, where 

 the deposits form so slowly that the 

 dust from space is not covered up, but 

 remains on the surface of the bot- 



tom. 



