1877.] 183 [McCrady. 



It may be, however, that notwithstanding the apparent irrecon- 

 cilability of the two hypothesis, there is no real incompatibility 

 between them. 



The course of development is always one of polarization, and we 

 cannot deny it to be in a large sense a polar force; yet this view of 

 its character is not inconsistent with the highest pneumatico-psycho- 

 logical interpretation of its processes — and consequently cannot be 

 inconsistent with the ordinary conception which represents the vari- 

 ous coordinated movements of an Amoeba as acts of volition, either 

 conscious or unconscious. I once watched the behaviour of an 

 Amoeba, which I shall call A. ubiquifluens , when it seemed to be 

 hesitating between the choice of several different routes of travel 

 across the field of the microscope. Several differently directed pseu- 

 dopodial lobes were put out, apparently towards special surrounding 

 objects, as if they were extemporized sense organs of unknown nature. 

 It occurred to me that in the absence of special sense organs, the 

 determining cause of the issue of these lobes might be an attractive 

 influence exerted by the surrounding objects upon the protoplasm of 

 the animal, which nevertheless might exercise a choice or selection 

 between the various solicitations of different objects. This it seemed 

 finally to do, when after an interval of indecisive repose, all the lobes 

 but one would be withdrawn, and the whole body move rapidly in 

 the direction of the persistent lobe, which of course would be that 

 turned toward the selected object. The existence of such an im- 

 pressibility of protoplasm in the amoeboid condition by surrounding 

 objects, would be nothing extraordinary when regarded as a sort of 

 equally distributed sense common to every portion of the protoplasm, 

 and the objects themselves would in this view be the sources of the 

 proper stimuli of this sense. Similarly, the presence of a yolk to 

 be assimilated may be conceived to evoke such a response from the 

 protembryo as is practically identical with a polarization of its proto- 

 plasm. 



We are, however, upon the threshold only of this great inquiry, 

 and must await the progress of research. 



The view suggested by Mr. Mi not as to the significance of the 

 expulsion of the Richtungsbl'aschen, is one which never occurred to 

 me, and is worthy of serious consideration. We may hope that it 

 will be tested by its originator in a series of investigations which can- 

 not fail to be of very high interest, however they may result for his 

 hypothesis . 



