374 NATURAL SCIENCE. dec. 



plants the cell is a very real and useful conception, and regarded 

 merely as a chambering of the protoplasm necessitated by increase in 

 size, differentiation, and need for support, will lead to no misunder- 

 standings. 



It is interesting to note that the coenocytic condition occurs in 

 certain stages in the life-cycle of completely septate plants. The 

 endosperm, or tissue produced in the embryo-sac, which in the 

 gymnosperms is the sexual individual bearing the female organs, is 

 in its first stages non -septate, and though generally becoming com- 

 pletely septate, may remain incompletely so. A similar free cell- 

 formation characterises the early development of the oospores of the 

 cycads. 



The Reign of the Nucleus. 



As in general botany and zoology, so also in special cellular 



histology, modern attention is being more and more concentrated upon 



the nucleus. It is unnecessary to do more than glance through the 



illustrations of scientific journals to see that new discoveries and new 



theories alike refer to the nucleus. In the case of cell-division, the 



opinion is growing that the changes begin in the nucleus, and that the 



apparent changes in the protoplasm are due to forces radiated out 



from changes in the nucleus. The centrosphere, the spindle, and so 



forth, more and more are being regarded as the visible results of such 



action of the nucleus upon the protoplasm as a magnet has upon 



sprinkled iron filings ; although, it must be admitted, there are still 



many observers who interpret the " centrosome " as a special organ 



of the "cell," and among these, judging from the "Atlas" to which 



we allude later. Professor E. B. Wilson must be included. In the 



matter of fertilisation, almost everyone now agrees that what was 



regarded as a cellular matter is really a nuclear matter. It is 



the nucleus of the spermatozoon that unites with the nucleus 



of the egg : and apparently the protoplasm of the body of either 



the male or female cell is indifferent to the result. As we know, 



in theoretical questions very great importance formerly given 



to cells is now transferred to nuclei. Weismann originally spoke 



of germ-cells : now he speaks of germ-plasma, meaning by that 



nuclear matter. The continuity of the germ-plasm now for him 



means, not the existence of a chain of cell-division, of which the 



successive generations are pendants, but the continuity of nuclear 



material. Instead of the early separation from the fertilised egg of 



germinal cells, he speaks of germ-tracks, along which the undisinte- 



grated germ-plasm is handed. In Hertwig's criticism of Weismann, 



where the question of "heirs-equal" or "heirs-unequal" (Natural 



Science, vol. v., pp. 132, 184) division occurs, the argument turns 



upon the nucleus, although the cell, rather than the nucleus, is 



spoken of. 



