1 4 EI SEN. [Vol. XV 1 1 . 



order to be able to assume its proper position near the equa- 

 tor of the cell, where it is most required. Again, the develop- 

 ment and the evolution of the cell require that as much as 

 possible the various parts should be arranged concentrically. 



Metaplasmic Secretions. — These secretions can be readily- 

 distinguished from the permanent elements of the cell by 

 proper methods of staining. Among the methods which I 

 have used there are only two which have proven of value. 

 One is the Flemming triple stain, the other is the iron-haema- 

 toxylin stain, with an after-staining with congo. The latter 

 method is much preferable, and it may almost be considered as 

 a specific stain for the secretions from the spheres. It has 

 already been stated that the ultimate visible structure of the 

 spheres consists of granules and that they are arranged around 

 alveoles. It is these alveoles which contain the metaplasmic 

 secretions, and the only way to explain their presence is to 

 assume that they are secreted from the granula of which the 

 spheres are composed. The secretions appear only in the 

 alveoles, and when these are scattered during mitosis they 

 carry the secretions with them. Even with the highest op- 

 tical powers no structure can be perceived in the secretion. 

 During the metaphase the alveoles, together with their secre- 

 tions, are found in the vicinity of the equator where the new 

 cell membrane is to be formed. The secretions from the 

 granosphere, and perhaps some of its granules, are used up 

 in the formation of the central spindle. At least the granules 

 lose, at this time, their intense staining capacity, diminish in 

 size, and cannot be followed any longer with any certainty. 

 Fibers and rays, both from the central spindle and from the 

 spindle cones, are frequently found ending in alveoles filled 

 with metaplasmic secretions, as if they were receiving nourish- 

 ment from them (Figs. 41, 42, 45, 61). 



The metaplasmic secretions teach us, among other things, 

 that the two spheres are structures independent of each other, 

 that one sphere is not a modification of, or a secretion from, the 

 other, but that each is of a distinct nature. When the spheres 

 reconstitute they do not do so together, but often in different 

 places of the cell, later on to be joined together. 



