96 The Conditions of Infusorial Life. 



diffusion of modifications" appears to be an assumption made to 

 suit the hypothesis — not the observation of a fact ; and if true, 

 it might supply the conditions necessary for the development 

 of different germs. 



Passing over a variety of experiments that are well worthy 

 of attention, we come to M. Pouchet's remarks on the scum, or 

 pellicle, which makes its appearance on the surface of infusions, 

 and which he calls the " proligerous pellicle" (pellicule pro- 

 ligere). This pellicle, he asserts, is composed of the "debris" 

 of "animalcules," at first of the lowest kind, afterwards of 

 higher grades. He gives it the epithet " proligerous" because 

 he considers it to play the part of " an improvised ovary which 

 produces the animalcules ;" how those previously formed were 

 produced he does not so clearly explain. Of these pellicles he 

 discovers several kinds : — 1 . The granulated pellicle, composed 

 of the carcases of monads and bacteriums. 2. The matted pel- 

 licle, formed by the interlacement of the bodies of long vibrions. 

 3. The pseudo-cellular pellicle, which appears after the genera- 

 tions of small monads and vibrions have passed away, and is 

 composed of deceased kolpods, or great monads. 4. The com- 

 posite pellicle, in which the previous elements are combined. 

 In confirmation of his views, M. Pouchet quotes Dumas to the 

 effect, that if a piece of flesh be left in water, it is resolved into 

 minute organic particles which exhibit spontaneous motion, and 

 which combine to make more complicated forms. A similar 

 observation was made by Mr. H. J. Clarke, of Cambridge, U.S.,* 

 who states that on watching the decomposition of a proboscis of 

 a young Aurelia flavidula (a jelly-fish), he observed the whole 

 of the component cells in violent agitation, like a single layer of 

 shot shaken in a flat pan, each cell appearing like a monad, 

 when the inner wall fell to pieces, and they scattered in various 

 directions ; others looked like chilomonads, and others like hexa- 

 mita. The same observer affirms that the fibrillas of the decom- 

 posing muscle of a Sagitta looked and behaved like vibrions, and 

 that Professor Agassiz verified his experiments. In conclusion 

 he remarks, c ' I do not pretend to say that everything that comes 

 under the name of vibrio and spirillum is a decomposed muscle 

 or other tissue, although I believe such will turn out to be the 

 fact ; but this much I will vouch for, and will call on Professor 

 Agassiz to witness, that what would be declared by competent 

 authority to be a living being, and accounted a species of vibrio, 

 is nothing but absolutely dead muscle." 



The preceding account of M. Pouchet's labours will suffice 



to demonstrate that they possess great value, quite independent 



of the particular theory which he has so ardently espoused. 



Let us now devote a few moments to some counter-experiments 



* Annual of Scientific Discovery for 1860. (Boston.) 



