105 pringshkim's researches on chlorophyll. 



is a contracted plasmodium-iiet, in wliich are embedded, as 

 in a matrix, small dense granular or globular bodies. 

 These, especially, are deeply stained by the iodine 

 (fig. 18). If the protoplasm lining the wall was origin- 

 ally thick they are numerous ; if it were thin they are few in 

 number, sparingly distributed, and may be almost absent. 

 But their number depends on the species examined, as well 

 as upon the thickness of the utricle. In the insolated cells 

 one can recognise with certainty a diminution in the num- 

 ber of these small bodies. In them is doubtless to be recog- 

 nised the element that so readily takes up oxygen under 

 the influence of light, and by its combustion causes the loss 

 of substance in the protoplasm, whereon depends the dimi- 

 nution in contracting power. It is often difficult to deter- 

 mine the loss of protoplasmic substance, anl it can only be 

 done by careful comparison of insolated and non-insolated 

 cells. 



Other striking changes after insolation in the protoplasm 

 have already been referred to as occurring in Spirogyra and 

 in Nitella. In the former there is the displacement of the 

 nucleus, vesicular swelling of the central plasma concurrently 

 with a granular coagulation of its substance and the occa- 

 sional colouring of the same, and finally, the rupture and 

 knotting of the protoplasm threads. In the latter there is 

 the ao-gregation of the streaming protoplasm at the area of 

 insolation, &c. Many of these changes doubtless occur in 

 general death of protoplasm from other causes besides light, 

 for example, from heat or electricity, and it is therefore 

 difficult, if not impossible, to distinguish amongst them the 

 specific action of light. 



Amongst the phsenomena which fall to be noticed here is 

 paralysis of protoplasm, or temporary stoppage of its 

 movement by light. If insolation be interrupted just at 

 the moment when the motion ceases, in many cases 

 the movement will sooner or later recommence and go on 

 normally. This may be observed in all kinds of movements, 

 alike in the motion of granules in the protoplasm between 

 the chlorophyll-bands of Spirogyra, in the circulation in 

 Tradescantia hair-cells, and in the rotation in Nitella. The 

 condition of paralysis in the cells of staminal hairs of 

 Tradescantia virginica, and in suitable (short) cells of 

 Nitella, may develope long before they are. decolorised. 

 Careful study of the gradual cessation of movement in 

 intense li^^ht convinces one that the light at the place where 

 it reaches the protoplasm creates directly a hindrance to the 

 movement, a fact explicable by the changes (just described; 



