CYTOLOGISCHE STUDIEN. 285 



laboratory at Bonn. It is a noteworthy fact that of the latter five 

 are Americans, and only two Germans. 



The first paper, " Ueber Entstehung der Karyokinetischen 

 Spindel bei Equisetum," by "W. J. V. Osterhout, is the most 

 complete account hitherto published of the development of the 

 karyokinetic spindle in plants, and hence is a very important 

 contribution to cytology. The origin of the spindle was traced 

 in the pollen mother-cells of Equisetum limosum. Briefly described, 

 the results of his observations are as follows : — The cytoplasm is 

 first found arranged as a network with fairly large meshes ; these 

 become elongated and converted into threads, which run parallel to 

 the surface of the nucleus, and later these threads arrange them- 

 selves at right angles to the nuclear wall. They then gradually 

 form themselves into groups, irregular multipolar spindles being 

 then produced. These multipolar spindles have been described 

 before by Belajefl:" and others as stages in the development of the 

 spindle, but their exact origin has never before been traced. The 

 next stage is the disappearance of the nuclear wall, and then the 

 formation of the normal bipolar spindle by the fusion into two of 

 the numerous poles. 



The second paper, by David M. Mottier, deals with nuclear 

 division in the pollen mother-cells of a number of Monocotyledons 

 and Dicotyledons. The author is the first to make a good com- 

 parative study of nuclear division in pollen mother-cells ; he also 

 investigated one gymnosperm, Finns Laricio. One of his important 

 observations was the development of the spindle, in which, as far 

 as he goes, he confirms Osterhout. In all the plants studied he 

 observed in the later stages of the spindle that, excluding the 

 fibres which radiate from the poles to the periphery of the cell, the 

 spindle itself consists of two sets of bundles of fibres. These two 

 sets consist of bundles of fibres attached one to each chromosome 

 (zugfasern), and of other bundles stretching from pole to pole 

 (leitfasern), each in connection with a chromosome. Thus by a 

 comparative study this theory of the mechanism of chromosome 

 movement is for the first time placed on a firm basis. Mottier 

 came to the conclusion that the synapsis condition of the nucleus 

 described by Moore and Farmer is an antefact ; it must be pointed 

 out, however, that Miss Sargant has observed this condition in the 

 fresh state, and her observation seems fairly conclusive. His most 

 important observations are, however, those of the behaviour of the 

 chromosomes. As he points out, it is almost impossible to under- 

 stand this merely from examination of them when they are attached 

 to the spindle ; the only trustworthy method is to follow out their 

 development step by step from the prophase onwards. Pursuing 

 this method, he confirms the observations of Belajefl' and Farmer, 

 though with a few modifications ; he leaves no doubt that there is 

 an actual longitudinal splitting of the chromosomes in the first 

 division. He puts forward, however, the view that in the second 

 division there is no longitudinal division, but a transverse splitting 

 of the chromosomes : but the evidence for this is exceedingly slight. 

 It is to be regretted that Mottier should have put forwnrd a view of 



