STRUCTURE.] THWAITES's THEORY. 45 



"But treating the subject of the functions of the cell- 

 membrane in a chemical point of view, we know that consider- 

 able chemical changes are taking place during the processes 

 of assimilation, secretion, elaboration, &c., and that these 

 are essentially chemical phenomena. Are we to look to an 

 organ of such a low chemical constitution as cell-membrane 

 as likely to give origin to the initiative in these important 

 changes ? I cannot believe such can be the fact, but that the 

 organ or substance which gives a start, as it were, to these 

 phenomena, will be found to be one in which rapid chemical 

 change is taking place one which, under the influence of 

 light, &c., acting upon substances brought into contact with 

 it, brings about a change in these ; these changes again react- 

 ing upon itself. I cannot help believing that such will prove 

 to be the explanation of the various phenomena of animal 

 and vegetable growth. On a chemical difference in the 

 constitution of this primary organ, a difference not likely 

 ever to be appreciable by chemists, any more than micro- 

 scopists will ever be able to discern the ultimate atoms of 

 bodies, may possibly depend the endless variety of forms 

 put on by organic nature. From a germ of great external 

 similarity they all alike originate ; but that these germs are 

 not really alike is shown by their subsequent behaviour. 

 They have different properties : does not this imply a different 

 constitution ? a different chemical constitution ?" 



This theory of Mr. Thwaites has lately received fresh sup- 

 port from an observation by Dr. Dickie, of Aberdeen, (Notes 

 on Alga, p. 10), that the cells of Hsematococcus binalis, a 

 beautiful Brittlewort (Diatomacea), have, when fresh, a power 

 of rotation in the interior of the mucous matter which sur- 

 rounds them ; a phenomenon which Dr. Dickie compares to 

 the revolution of the yolk in the ova of certain Mollusks, 

 as was observed long ago by Leuwenhoek. 



The bladders of cellular tissue are destitute of all perfora- 

 tion or visible pores, so that each is completely closed up from 

 its neighbour, as far as we can see ; although as they have 

 the power of filtering fluids with rapidity, it is certain that 

 they must abound in invisible pores, and that they are not 



