Dixon — Nuclei of the Endospenn of Fritillaria i/jiperialis. 723 



dissolve, the nucleoli disappear prior to the formation of the spindle 

 points undoubtedly to, at least, a partial nucleolar origin of the latter 

 structure ; ^ this view finds further support from the fact, in those 

 cases of simple direct fission in which the spindle is not formed (fig. 

 13), the nucleoli usually persist during the process of fission. However, 

 the dimensions of the nucleolus, before division, appears to bear no 

 relation to the distinctness of the spindle formed during division ; for 

 often during normal karyokinesis in the embryo-sac, before tlie 

 protoplasm is partitioned into cells, the spindles of the dividing nuclei 

 are very indistinct, while, before division, the nucleoli of these nuclei 

 were both large and numerous. 



Very often the connecting neck between the two daughter nuclei 

 is so delicate (fig. 7) that it is difiicult to distinghish it from a 

 retarded chromosome of normal karyokineses (fig. 8). However, in 

 those cases, where retarded chromosomes form a connection between 

 the daughter nuclei, the latter do not reconstruct themselves completely 

 {e.ff. do not form their nuclear membrane) till all the chromosomes in 

 connection with them are retracted. Whereas in the other case the 

 daughter nuclei, while still in connection with one another by means 

 of the narrow neck, resemble resting nuclei except for the fact that 

 they possess definite protoplasmic radiations and the spindle lies 

 between them. 



During these divisions portions of the nuclear thread (chromo- 

 somes ?) protude from the daughter nuclei and project into the 

 surrounding protoplasm (figs. 6 and 9). In no case was I able to 

 detect longitudinal fission of the chromosomes during direct division. 

 However, the manner in which two pairs of chromosomes, sho"\vn 

 beneath the connecting neck in figure 6, are in contact with one 

 another, suggests the thought that they have been foimed by longi- 

 tudinal fission. 



Tripolar and quadripolar nuclei are frequently to be found in these 

 preparations, and in many cases these multipolar nuclei divide into 

 three or four daughter nuclei (figs. 10 and 11). Usually one of the 

 poles appears to have feebler attractive powers than the others, and 

 consequently the nucleus formed at it is small, since but few chromo- 

 somes are drawn to form it from the common nuclear plate. Again, 

 cases are found in which two of the poles coalesce, and round them the 

 majority of the chromosomes assemble, leaving for the other pole or 

 poles, but very few (sometimes only two to four). The variation in the 



' Cf. Strasburger, Karyokinetische Probleme, Jahrb. f. wiss. Bot. 1895. 



