318 SUMMARY OF CURRENT RESEARCHES RELATING TO 



present considerable enlargements or diminutions in size, but that 

 they are either all of the same thickness, or only here and there 

 present variations, and these of the very slightest character. There 

 is no compact plate in the equatorial plane, but only closely packed 

 coils ; in this plane there is frequently to be observed a clear medulla, 

 the presence of which appears to have escaped the notice of Stras- 

 burger. After carrying these criticisms further, attention is drawn 

 to many points in which there is a resemblance between the cells of 

 the tissues of animals and plants. 



Further studies have been made on karyokinesis and the structure 

 of the nuclei. As to the latter, we may note that the author finds 

 that what he has called the " intermediate substance " of the nucleus 

 contains, after treatment with reagents, and probably also during life, 

 a fine continuation of the nuclear network. The fine granulation 

 which may be seen in the intermediate substance of the nucleus with 

 less powerful lenses, and which was formerly thought to be due to 

 coagulation in a homogeneous mass, is to be referred to this fine frame- 

 work ; the bars, so to speak, of which it is made up are the direct 

 continuation of the coarser, and are chromatic. It is, perhaps, to the 

 presence of these that we have to refer the possibility of colouring 

 the intermediate substance of the nucleus. The nuclear envelope, so 

 far as it is capable of being coloured, consists of small peripheral 

 enlargements of these bars, and is formed of the same substance as 

 they are. The question whether there is an achromatic membrane 

 enclosing the nucleus cannot yet be decided. 



After giving some account of the polar corpuscles, Flamming 

 points out that the angles of the filamentar loops, which go to form 

 the stellate chromatic figure, are often distinctly in contact with one 

 of the achromatic fibres ; the j^aleness and fineness of the latter are so 

 extreme that never more than a part of them has ever yet been 

 detected ; from what he has seen, however, he concludes that this 

 touching of a chromatic loop with an achromatic filament corresponds 

 to the natural position. It would follow, therefore, that the angle of 

 the loop has been attracted by the filament, and that later on the 

 looj^s, when the mother-figure divides, would become arranged in two 

 groups. 



In some examples of the star or circlet-forms the chromatic fila- 

 mentar loops lie so freely that they can be counted, with the aid of 

 oil-immersion objectives and Abbe's illuminating apparatus. In the 

 epithelial cells of the buccal and branchial epithelium of the larvae of 

 salamanders four-and-twenty loops were in three cases quite dis- 

 tinctly made out. In other cases from 17 to 22 were less distinctly 

 seen, and the possibility is that in these cases there were really 24 

 filaments also. 



Dealing lastly with some observations on cell-division in Man, 

 it is stated that in the epithelium of the cornea of an adult subject, 

 the lowermost layers exhibited rare and scattered cell-divisions, but 

 here again, just as in Salamandra maculata, the chromatic figures were 

 detected, but the achromatic could not be seen, so small was the 

 object. In the blood of a leucocythaBmio patient cell-division with 



