14 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



and finally redisijosed according to its original bearings, as if guided 

 by an unseen magnet ; most of the loops, subject to slight irregularities, 

 being turned round in the same general direction. The free ends of 

 the legs of the loops at first point peripherally ; as the monaster 

 changes into the equatorial plate, this position is reversed. But 

 again, in the daughter-nuclei, the loops have their corners directed 

 towards the centres of the nascent cells. The regressive stellate 

 figures lead to the formation of coils by coalescence of the ends of the 

 segments ; the coil becomes denser ; the chromatin and achromatin 

 are reblended, and the resting phase of the completed daughter- 

 nucleus results. 



The most striking attendant (if it be not an essential) pheno- 

 menon of division is the longitudinal splitting of the nuclear fila- 

 ments. This splitting may occur both previous to and during the 

 phase of the progressive stellate figure ; in the corresponding 

 regressive phase the filaments are reduced in number, as if longi- 

 tudinal coalescence of the split fragments of the nuclei had taken 

 place. A few daughter-cells, with two stars, offered apparent excep- 

 tions to this law. How to distinguish between the more essential 

 and less general phenomena of nuclear change, is a question which 

 extended researches are required to answer. Some equatorial plates, 

 previous to the diaster-phase, exhibit union of the loops, then 

 arranged in two apposed groups. Flemming regards such union as 

 secondary. The continuity, believed to be general and primitive, 

 noticed by some observers in the filaments of nuclear spindles, hence 

 originally so termed, obtains only as to the pale achromatic threads 

 (Strasbui'ger's " cell-threads," a phrase which Flemming would 

 retain). Of these achromatic figures, because of optical difiiculties, 

 very little is known. It so happens that they are exceptionally con- 

 spicuous in certain vegetable cells, copiously and carefully studied by 

 Strasburger, and in the ova of various animals, subjects of the earlier 

 investigations of Biitschli, Fol, and Hertwig. On these researches 

 were based views of the constitution of dividing nuclei, which have 

 since received notable modifications, both from their authors and 

 others. If, with Flemming (and Klein), we deny that coloured 

 nuclear filaments ever arise from the growth of granules, we may also 

 conclude that the chromatic elements always lie outside, and nowise 

 in the course of, the achromatic threads. The two series of figures, 

 chromatic and achromatic, are quite distinct. Their varying pro- 

 portions in each nucleus may be one of the most important sources of 

 difiference between different cells. The achromatic figure is no less 

 significant than the chromatic. Its filaments are doubtless connected 

 with other pale threads, traversing the extra-nuclear protoplasm. 

 That forces, seated in the achromatic component of the nucleus, 

 are the real initiators and directors of division, Flemming regards 

 as more likely to be true than any other hypothesis we can formulate. 

 The function of the nucleoli has in this respect been greatly mis- 

 taken. Better methods may show that they are not even morpho- 

 logical constituents, but mere thickenings or deposits {Ahlagcrungen 

 = sequcslratu, or things put aside). Flemming's bold conjecture, that 



