116 Transactions of the Royal Microscopical Society. 



larger ultimate molecules. This being the case, we may feel per- 

 suaded that particles of organic matter, like the spores of many 

 living organisms scarcely visible with the highest magnifying 

 powers, and, if seen, quite undistinguishable from one another, 

 might yet differ in an almost intinite number of structural 

 characters, just as any number of different newspapers in various 

 languages or with varying contents would look alike at the distance 

 of a third of a mile. 



3. General Conclusions to he deduced from the above Facts. 



When we come to the application of these principles to the 

 study of living matter, we are immediately led to feel how very 

 little we know respecting some of the most important questions 

 that could occupy our attention — questions which certainly never 

 presented themselves to me, until I looked upon them from this 

 point of view, and which perhaps have not occurred to anyone 

 before. As illustrations of the subject now under consideration, 

 I do not think I can select better than the facts bearing on 

 the size ani character of minute germs, and on Darwin's theory 

 of ultimate organized gemmules, as described in Part ii. chapter 

 xxvii. of his work on the variation of animals and plants under 

 domestication. So far as I have been able to learn, he has nowhere 

 given any opinion as to the probable size of such gemmules, nor 

 discussed the probability of some of his speculations when examined 

 from a numerical point of view, and in connection with the pro- 

 bable size of the ultimate molecules of organized matter. I there- 

 fore propose to do so ; since, though not actually a microscopical 

 question, it is most intimately connected with our studies, and as 

 microscopists I think we have a good claim to investigate objects 

 that are just beyond our magnifying powers. 



For the sake of simplicity I will take into consideration only 

 the albuminous constituents of animals, using the term albumen 

 in a sort of generic sense, to include many compounds, which differ 

 in many particulars, and yet have many in common. With slight 

 modifications the same principles would apply in the case of other 

 substances. Whatever be the special variety of this constituent, it 

 is so associated with water in living tissues that in most, if not in 

 all, cases they would cease to live if thoroughly dried. This is 

 exemplified by the case of hair and horn, which must contain much 

 water at the growing end, but are dead where hard and dry. In 

 living tissues much of the water is no doubt present simply as 

 a liquid mechanically mixed with the living particles, but it appears 

 to me that we ought to look upon some portion as being in a state 

 of molecular combination. So little attention has been directed to 

 this kind of weak affinity, that its very existence is almost or quite 



