ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 223 



limits. It is a condition of rest par excellence in the life of the cell. 

 It is interrupted by the action of a new factor — the longitudinal splitting 

 of the chromatin elements. The author seeks to justify his regarding 

 this as "an independent expression of life, a reproductive act in the 

 chromatin elements." 



(6) The nuclei of the two first segmentation spheres are discussed in 

 the next chapter. The reconstructive processes and the individuality of 

 the nuclear elements are especially treated. " The general agreement 

 in the number and disposition of the chromatin elements before and 

 after the resting stage of the nucleus, makes it probable that each 

 element of the daughter-plate is identical with an element again pro- 

 duced from the nuclear framework. This is confirmed by the demon- 

 stration that (1) each new end of a chromatin loop is identical with an 

 end of the loops forming the nucleus, and (2) each two ends, united 

 before the reconstruction in one element, are after the retraction of 

 the framework again united in one loop." The only question is about 

 the middle portion uniting the two ends. If the hypothesis is correct, 

 then of the four chromatin loops, observed in the division figure of a 

 segmentation cell, two are derived from the male and two from the 

 female. The importance of this in regard to heredity, is emphasized 

 by the author. 



(7) Archoplasma and Centrosomata in the two primary segmentation 

 spheres are discussed in the next chapter. The presence of the centrosoma 

 (in itself an important fact), its division, the modification and disposition 

 of the archoplasma, are discussed. The last chapter (8) on abnormal and 

 pathological phenomena is rich in suggestions as to the physiology of 

 the cell-division. An appendix unfavourably criticizing Kultschitzky's 

 results concludes this valuable memoir. 



Maturation and Fertilization of Ova in Ascaris marginata.*— Dr. 

 N. Kultschitzky follows up his recent investigation of the phenomena of 

 maturation and fertilization in Ascaris megalocephala by a similar study 

 of Ascaris marginata. His general results are thus summed up : — 



(1) In the first stages of development, he shows that the chromatin 

 of the germinal vesicle, and the (paler on staining) substance of the 

 nucleolus arise from the same source. This confirms an opinion long 

 since expressed by Flemming. 



(2) The mature ovum has the following characteristics : — (a) the 

 chromatin of the germinal vesicle becomes a group of rods, variable in 

 size and number ; (h) the other constituents entirely disappear ; (c) an 

 egg-envelope may be developed, but only fully after fertilization, never 

 perfectly in unfertilized ova. 



(3) The achromatin substance forming the spindles in polar globule 

 extrusion arises from the protoplasm of the ovum, as in every other 

 division of the egg-cell. 



(4) The extrusion of polar globules is a genuine typical process of 

 indirect (" karyomitotic ") division, and the extruded elements are to be 

 regarded as cells. 



(5) The structure of the pronuclei deviates considerably from the 

 general type of nucleus. Its framework is formed of achromatin sub- 

 stance, which with the membrane determines the form. In other nuclei 



* Arch. f. Mikr. Anat., xxxii. (1888) pp. 671-82 (2 pis.). 



