102 Transactions of the Society. 



On the Nomenclature of Cell-Division. 



Cell-division therefore involves at least three operations — that 

 of the careful division of the chromosomes ; and that of the irregular 

 sorting out of the mitochondria and of the Golgi elements into 

 two subequal portions. The words " karyokinesis and mitosis " 

 refer to the chromatin ; it seems advisable to use the words " cell- 

 division," "cytokinesis " to mean all three processes, karyokinesis, 

 dictyokinesis and chondrokinesis, as below : — 



[Karyokinesis and Mitosis (Chromatin) 

 Cell-division or Cytokinesis i Dictyokinesis (Golgi apparatus) 



( Chondrokinesis (Mitochondria) 



It has now been shown in one form at least {17), that during 

 the development of the embryo every cell which divides not only 

 undergoes karyokinesis but also dictyokinesis and chondrokinesis, 

 and the latter processes are probably as universal as karyokinesis. 



It is important to notice that karyokinesis, dictyokinesis and 

 chondrokinesis are all preceded by the division of the centrosome, 

 though the latter is possibly stimulated to divide by the nucleus. 

 To bring the process of division of the centrosome into line with 

 the above nomenclature, it might be called " centrokinesis," from 

 Kevrpov, and Klvr]ai<i, change. 



Lecithin and Yolk-Discs and Spheres. 



The zoologist meets lecithin in the form of yolk-discs, and these 

 structures are familiar to all who have studied amphibian, avian, 

 and other material, where they exist in the form of flattened 

 rounded discs, which may turn quite black in osmium tetroxide 

 fixatives. The chemical elements of yolk have been accurately 

 examined, especially in the hen's egg, and in the yolk of the latter 

 one finds fats, protein, lecithin and cholesterin. The yolk of 

 amphibia and other vertebrates is undoubtedly a compound body, 

 like that of the avian egg ; this is a very important point to be 

 remembered. Chemically, lecithin itself may be looked upon as 

 phosphorized fat, and it has many of the properties of fats, but it 

 contains, in addition to phosphoric acid, choline. Lecithin, like 

 fat, is soluble in alcohol and ether, but is insoluble in acetone, 

 which dissolves fat. Mann showed long ago that lecithin crystals 

 go from yellow to brown in osmic acid solution, never black, and 

 this would indicate in the case of oleo-lecithin that in combina- 

 tion the reducing property of the olein is lost. In early or newly 

 forming yolk-discs of such widely different animals as the snail 

 and insect, no amount of soaking in 2 p.c. osmic acid will cause 

 the black colour to appear. Older discs will however gradu- 

 ally turn from yellowish to brown, and still older or mature discs 



