554 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Finally, a second longitudinal division of the filaments takes place in 

 the daughter-cells during the D/as/er-phase. 



In the homoeotypical form the divided filaments, after separating 

 from one another, during metakinesis, remain for a long time in the 

 region of the equator. The appearance of the figures might lead to the 

 erroneous opinion that there had been no longitudinal fission of the 

 filaments. 



The number of primary segments is, in both types, only half of that 

 which it is in the mitosis of other kinds of cells of Salamandra (twelve 

 instead of twenty-four). All the diflerences are reduced to one chief 

 fact — the prolongation of the process united to a special form of 

 metakinesis, that is to say from that phase in which the unfolded 

 segments separate from one another to form tho two groups of daughter 

 figures. These special forms are found, with very similar characters, in 

 the egg of Ascaris (according to Van Beueden), and probably (according 

 to Carnoy) in the spermatocytes of Arthropoda. As yet they have only 

 been found in sexual cells. 



These observations throw light on the remark of Carnoy that the 

 characteristic phenomena of karyokincsis are variable and that no case 

 appears to be essential. It is possible that in the small spermatocytes 

 of Arthropods the first longitudinal division of tho filaments escaped 

 Carney's notice, and so led him to a generalization which Flemming 

 shows to be inexact. 



Cell-division.* — Dr. T. Schottlander reports the results of his re- 

 searches on nuclear and cell-division in the endothelium of the inflamed 

 cornea. His principal conclusions are as follows : — 



(1) In some cases irritation of the frog cornea by chloride of zinc 

 simply causes rapid decomjjosition of the endothelium. This happens 

 with prolonged irritation, or with weak animals. (2) With moderate 

 irritation and strong animals certain changes are seen from the second 

 day onwards, which seem to be progressive, and doubtfully suggest 

 amoeboid movements of the cells, or direct segmentation, or direct frag- 

 mentation. (3) From the seventh day the mitotic changes of regenera- 

 tion begin, and continue till the fifteenth day. 



(4) Tho mitoses are for the most part typical. Tho anaphases are 

 remarkable for the splitting of the achromatic connecting threads, which 

 appears to mark the completion of division, and recalls the cell-plate 

 formation in plants. (5) Various abnormal cellular figures occur, 

 especially characterized by varied disposition of the chromatic loops. 

 (6) Multiple nuclear division rarely but really occurs, both in regular 

 fashion and with certain irregularities of procedure. (7) Among the 

 deviations from the typical mitosis must be noted certain figures which 

 may possibly represent indirect fragmentation. 



Karyokinesis and Heredity, f — Prof. W. Waldeyer has lately pub- 

 lished a series of papers on the phenomena of karyokinesis and their 

 relation to the problems of heredity. He confines himself for the most 

 part to a summary of past researches, in which the results and 

 divergences of Hertwig, van Beneden, Nussbaum, Carnoy, Weismann, 



* Arch. f. Mikr. Anat., xxxi. (1888) pp. 426-82 (1 pL). 



t ' Ueber die Karyokinese und ihre Bedeutung fiir die Vererbung,' Leipzig, 

 1887. 



