THE BEGINNINGS OF LIFE. 279 



gelatinous layer in which they had been imbedded 1 . 

 They do not, however, resume their active movements 

 of translation. They merely exhibit more or less rapid 

 oscillations, which, although quite compatible with life, 

 differ in no important respect from the Bro<wnian move- 

 ments which would be displayed by similarly-light not- 

 living particles. 



It is the presence of the gelatinous material which 

 gives consistence to the pellicle, and makes the name 

 c primordial mucus, 3 bestowed upon it by Burdach, more 

 suitable than it would otherwise have been. 



1 Whilst agreeing with Cohn so far as this observation is concerned, 

 I by no means agree with him in his general estimate of the life- 

 history of the Bacteria. On account of their existence in the above- 

 named jelly, more especially, he came to the conclusion that Bacteria 

 , ere most closely allied to certain algse, composing the genera Palmella 

 and Tetraspora, which have a similar gelatinous stage of existence. 

 He considers that they have affinities with these on the one hand, and 

 with the Oscillatorice on the other. The gelatinous condition represents 

 the early stage in the life-history of Palmellce and Tetrasporce. In the 

 later stages the cells previously contained in the jelly loosen them- 

 selves, and become independent, free-swimming organisms. Cohn thinks 

 that a similar order is observed in the life-history of Bacteria. He 

 believes that these appear first in solutions as small jelly-masses, which 

 gradually increase, unite, and grow into a uniform pellicle, out of which 

 the Bacteria ultimately appear as free-swimming organisms. The real 

 order is, as I think, precisely the reverse. At first they are independent 

 bodies, in the form of minute moving organisms scattered through the 

 fluid. After a time they gradually accumulate in the midst of the fluid, 

 or, more commonly, at the surface, and, becoming motionless, are found 

 to be imbedded in a pellucid jelly. What is the mode of origin of 

 this jelly whether it also merely accumulates at the surface, or whether 

 it is formed around and by the Bacteria in this situation nobody seems 

 to know, although the latter seems to be the more probable supposition. 

 It certainly is a most important constituent of the pellicle. 



