168 CHIRONOMUS PRASINUS. 



differentiation. Now, differentiation, we know, is always associated 

 with perfection of function. We are justified, therefore, I think, 

 in connecting the extraordinary secreting activity of the glands, 

 in the first place, with the complex structure of the nuclei of the 

 cells concerned in the process. 



But, again, there is another point, as I have mentioned, which 

 bears upon this subject. Under some conditions I have found 

 that the cells, instead of being simple in shape, as in Fig. 4, 

 assume the very remarkable forms exhibited in Fig. 8, where the 

 nucleus, with a certain amount of the protoplasm of the, cell, 

 becomes almost separated from the remainder, and projects into 

 the cavity of the gland as upon a pedicel, the remainder of the 

 cell assuming a flat, polygonal form. Now, here we find that the 

 nucleus, the centre of the vital activity of the cell (which vital 

 activity is here chiefly manifested in the act of secretion) is 

 removed into what I think we may regard as a speciallised portion 

 of the cell, both on account of its marked separation from the 

 remainder, and on account of its projection into the cavity of the 

 gland — i.e.^ into a position obviously the most favourable for a 

 copious outpouring of the secretion from its walls. The remaining 

 flat portion, or base of the cell, I regard as nutritive — />., it takes 

 from the blood, to which it offers a large surface, the material 

 requisite for the growth of the whole ; and the more so, as I have 

 occasionally noticed secondary nuclei in this part, evidences o^ 

 imperfect cell-division, showing that here the processes of growth 

 go on, but giving as yet no traces of the complex structure just 

 described. I think it possible that the pedicellated portion of 

 the cell, with its nucleus, becomes completely separated, and falls 

 off when its vital activity is exhausted and its mission accom- 

 plished, its place being taken by the new cells into which the 

 basal portion has by this time divided. We have, I think, in 

 these cells a differentiation of the nucleus, evident as a matter of 

 ocular demonstration, and another differentiation, equally real, of 

 the protoplasm, which can for the present only be a matter of 

 inference, but both contributing to the higher organisation of the 

 gland. 



