The Presidenfs Address. By H. J. Slack. 117 



Dallinger's drawing represented in the September number of the 

 new Journal, * we find the latter creature's body composed of two 

 oval beads, each one seeming only about the size of the nucleus of 

 the just mentioned flagellate monad, though the magnification is 

 1400 diameters greater. How much smaller living creatures may 

 exist it is not possible to say, but with those of these dimensions we 

 can scarcely expect any mode of vision furnished by the Microscope to 

 enable the processes of their germ formation to be traced. Another 

 difficulty of dealing with these organisms arises from the fact that 

 it is only by unintermittent watching for a long time and under a 

 variety of conditions that the whole cycle of their life changes 

 can be made known. Mr. Dallinger has shown in the case of 

 monads that the same species in difierent stages of development 

 present very difierent aspects and behave in very difierent ways. 

 The minute bacteria found to be capable of producing in animals 

 the splenic disease which the French call san^ de rate, has been 

 found by other observers able under certain conditions to branch 

 like the mycelium of a mould ; and in M. Pasteur's book ' La Biere ' 

 will be found many illustrations of dissimilar growths of ferments, 

 and fungi under difierent circumstances. After recounting many 

 interesting experiments, M. Pasteur remarks that in the dust of a 

 laboratory in which fermentations are studied, there are many germs 

 which give rise to organisms which it is impossible to distinguish 

 fi-om alcoholic ferments, although they do not possess the properties 

 of those bodies. 



In endeavouring to avoid the error of lumping together a 

 number of small organisms under a common heading, implying a 

 very low stage of development, attention should be paid to any 

 indications that may be obtained from their external organs, 

 although their internal structure may defy scrutiny. An or- 

 ganism furnished with cilia in constant vibration is in that 

 respect, and may be in others, below another in which cihary 

 motion, to use the words of the * Micrographic Dictionary,' " is 

 interrupted at intervals, apparently under the influence of a will." 

 Of course, the term " will " is only employed to express a remote 

 analogy. The difierence appears to be that the ceaseless motion in 

 one case responds to some contiuuous necessity, possibly that of 

 respiration, while the intermittent one responds to a less frequent 

 need, such as going in search of food. The " springing monad " of 

 Messrs. Dalhnger and Drysdale,t so called from its peculiar habit 

 of coiling and uncoiling one of its flagella with a darting motion, 

 not unlike the vorticella, carrying the body with it, evidently 

 possesses an instrument superior to the simple cilium, and the same 

 may be said of the " hooked monad " of these observers, a creature 

 " with a persistent hook-like flagellum." The " calycine monad," to 



* ' Juumal R. M. S.,' vol. i. No. 4. f ' M. M. J.,' vol. x. p. 245. 



