ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 219 



those lower organisms of whicli we cannot certainly say whether they 

 are animals or plants. We are fain to conclude that in the resting 

 cells also there is a typical agreement in structure. Yet the dif- 

 ferences are such as to forbid us from bringing all the phenomena 

 under one head. It is, nevertheless, worth while to try and reduce all 

 the various forms of nuclei to a common scheme. 



It is certainly not due to chance that young daughter-coils are so 

 extraordinarily like the first coils of the mother-nucleus ; as soon as 

 a nucleus begins to divide a polar and antipolar side become apparent, 

 and on the polar side there is a definite polar area ; the several regions 

 are characterized by the course of the filaments, which extend from 

 the antipolar side to the polar and into the polar area ; here they loop 

 round and return to the antipolar side ; the daughter-coils differ only 

 from the young mother-coils in having the filaments thicker and less 

 looped. This typical agreement is found in vegetable as well as in 

 animal cells. It is not conceivable that in the resting stages these 

 filaments disappear altogether ; after the formation of the nuclear 

 network some remain, and have essentially the same course as in the 

 coils ; from these " primary filaments " fine secondary lateral pro- 

 cesses are given off, and from these again, probably, tertiary filaments, 

 and so on. The several filaments may either unite with one another, 

 and at the nodal portions of the resulting network may collect to 

 form nucleolar structures. If these chromatin-masses become more 

 independent as compared with the nuclear plexus, they may give rise 

 to true nucleoli. 



If we allow this hypothesis we shall be the better able to under- 

 stand the phenomena of cell-division ; it is only necessary to suppose 

 that, at the commencement of an act of division, the chromatic sub- 

 stance streams along paths already formed into the primary nuclear 

 filaments. In this simple manner the mother-coil is formed. The 

 angle which the primary filaments form on the polar area has been 

 shown to be constant during the whole process of division, and to 

 pass directly into the angle formed by the filaments of the daughter- 

 coil. "When this last settles down to rest, the filaments throw out 

 lateral buds, which again send out processes ; along these buds and 

 processes the chromatic substance is more regularly distributed 

 through the whole of the nucleus. The division of the chromatic 

 substance of the nucleus is therefore ultimately due to a longitudinal 

 cleavage of the filaments, and Kabl thinks that if his hypothesis be 

 correct we cannot conceive of a more simple mode of nuclear division 

 than that which we do in fact observe. This view is not affected 

 by the supposition that the nuclear filaments consist of a single 

 substance, or by that of Strasburger, who thinks that there are 

 hypoplasmatic cords and interposed chromatic microsomes. 



The author points out that his view is supported by the well- 

 known fact that both the coarser filaments of the network, as well as 

 the nucleoli have an excentric position, and that there is never a 

 regular concentric or even radially concentric arrangement of the 

 chromatic substance in the nucleus. It is clear that very various forms 

 of nuclei must arise from differences in the development or retrogres- 



