The incipient nucleus 7 



and that the 'central body' is a slight concentration of the alveoli in the meshes of which 

 certain distinctive granules occur. This central concentration of the alveoli is really only 

 apparent, as it is due to the absence of vacuoles from the 'central body,' whereas vacuoles 

 cause a considerable breaking-down of the peripheral alveoli (consult fig. 5). 



From this mass of conflicting evidence it is possible to sift out certain 

 facts which hardly admit of dispute, and, if the whole question be carefully 

 considered in the light of probable misinterpretations due to optical illusions 

 and other causes, it is possible to arrive at conclusions which may not be 

 far removed from the truth. The majority of recent workers agree that 

 there is in the Myxophycean cell a structural differentiation (the so-called 



o.i. 



Fig. 5. Section through cell of Chroococcus macrococcus Babenh. showing the incipient nucleus 

 (i.r,.) and the small vacuoles (v.) in the cytoplasm. The fine reticulation of the protoplast 

 is also well shown. The outer line marks the limit of the ou^er integument or investment 

 (o.i.) of the cell, x 1000 (after a drawing by Miss Acton). 



' central body ') which from its position and relationship to the rest of the 

 protoplast is homologous with the nucleus. This body may be truly regarded 

 as an incipient nucleus 1 , and the disagreements as to the details of its 

 structure are probably due to two causes : first, to morphological misinter- 

 pretations; and secondly, to the fact that it does not exhibit a uniformity of 

 structure in the various members of the group. The Blue-green Algae 

 are undoubtedly very primitive organisms in which the protoplast shows the 



* It would be preferable to discontinue the use of the term ' central body,' as there is no 

 actual body with definite limitations. It is only a sort of concentration of varying degree of an 

 alveolar protoplasmic network in which certain granules (possibly of one of the ehromatin 

 substances) are lodged, and would best be openly recognized as an incipient nucleus. 



