ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 13 



A supplement to the first Section sustains the observations of 

 Treub, who in multinucleate vegetable cells saw all the nuclei 

 dividing at the same time. Flemming further holds that a like 

 simultaneity extends to the several phases of division. Cells from 

 the testis and binucleate cells from the gills of Salamanclra showed 

 this phenomenon. 



Having advocated the approximate universality of indirect division, 

 and the normal repetition of correspondingly similar phases, Flemming 

 in his second section gives a revised account of (1) the successive 

 phases which appear in well-observed cases, (2) the transitions from 

 one to the other, (3) the subsidiary phenomena which may attend the 

 principal changes, and (4) certain exceptional modifications of the 

 phases themselves or their intervening stages. Finally, he points 

 out (5) the directions in which we must look for a choice among 

 what seem the only possible hypotheses capable of explaining the still 

 wholly obscure conditions whereby rejuvenescence of the nucleus is 

 determined. The two extremes (the starting-point and the goal) in 

 the course of a complete division are the resting phases of (a) the 

 parent nucleus and of (b) the two daughter-nuclei eventually produced 

 therefrom. Half-way between these extremes lies the equatorial 

 plate, that phase which comes just before the very act of division, and 

 to which all the other phases are preparatory or consequent. Stras- 

 burger's " nuclear plate " not only designates this phase, but also 

 that which follows ; he further employs in the same sense the words 

 " nuclear barrel," or " nuclear spindle," which Flemming would 

 apply more definitely only to nuclei already advanced in division. 

 From the equatorial plate we pass on to the stellate figures, for 

 which are used Fol's terms monaster (parent phase) and diaster 

 (daughter phase), extended by Klein from the nuclei of eggs to those 

 of cells in general. Between the stellate and resting phases come the 

 coiled figures. Thus every cycle involves two series of changes — the 

 first progressive, from the parent resting phase to the equatorial plate, 

 the second regressive, from the equatorial plate to the final assump- 

 tion of the resting phase by each of the two daughter-nuclei. The 

 two series have like phases, but in reversed sequence. When the 

 parent nuclear plexus begins to change, it gradually takes up the 

 whole of the chromatin, while its filaments, growing thicker, become 

 disposed at nearly equal distances, and at length the coiled figure 

 results. Segmentation of the coil introduces the figure of the 

 monaster ; but the coil may assume the transitional form of a chaplet 

 (Kranzform), with little or no discontinuity. Every segment is a loop 

 [Schleife) shaped somewhat like the letter V, with a more or less open, 

 usually rounded, corner, and equal, or nearly equal, straight or 

 twisted legs. [By a curious coincidence, Flemming's own diagram 

 exhibiting the double series of nuclear phases has the same general 

 loop-like figure as each one of the visible elements of which the 

 dividing nucleus is itself composed.] In the constitution of the 

 stellate figures, and their passage to and from the phase of the 

 equatorial plate, the loops undergo very noteworthy alternate changes 

 of orientation. By these diastoles and systoles each loop is displaced 



