Tiii//nr: Neuromotor Apparattu in l\uj>/otes 455 



nuclei" (Mim-hiii. 1912. p. 1). Metazoan organs arc composed of many 

 cells which liavc become modified and often highly specialized to form 

 tissues, of which several kinds may appear in the same organ. On 

 the other hand, organs of the Protozoa are not composed of cells but 

 are modifications of a single cell. We might, therefore, regard the 

 protoplasm within the organs of the protozoan as having the same 

 general physiological properties as the protoplasm throughout the 

 protozoan body and these general properties should be possessed in 

 common with those of any protoplasm wherever found. 



Now one general property of all protoplasm is the propagation 

 throughout all its substance of an excitation effected by a stimulus. 

 The morphological continuity of this substance into all the parts or 

 organs of the protozoan body would appear to be the only essential 

 condition for the conduction of an excitation, wherever initiated, to 

 any such part or organ. If this condition is evident in all protozoans, 

 it would seem that specialized, conductive -structures for the trans- 

 mission of excitations were unessential and useless. Accordingly, 

 caution in ascribing a nervous function to a structure or a system of 

 structures in a protozoan body is justifiable. 



However, may not as much be said for other general properties of 

 protoplasm? Chambers (1917a) has shown that the surface layer of 

 marine eggs may be pulled out into long strands "without otherwise 

 disturbing the contour of the cell. On being released the strands tend 

 to curl and retract slowly until they disappear" (p. 6). Similar 

 phenomena may be readily demonstrated in the endoplasmic globules 

 of E. patella that frequently form with the escape of the endoplasm 

 into the water. Also, the proverbial amoeba and many of its relatives 

 display the phenomenon of contractility in normal behavior, as do also 

 all amoeboid cells of the Metazoa. And the cytoplasm of amoebae 

 possesses no fibrils or other specialized structures, so far as is known. 

 by which it effects contraction. Nevertheless, this general property of 

 the cytoplasm is not functioned by such simple and primitive means 

 in many protozoans. It is a well-established fact that in the so-called 

 higher forms contractility is effected mainly, though perhaps not 

 exclusively, by specialized structures, the myonemes. 



If, therefore, in the "unicellular" protozoan the general property 

 of contractility has become more or less localized in special organelles, 

 what should restrain conductive protoplasm from the specialization 

 of structures to facilitate conductivity? The extreme rapidity with 

 which many protozoans react to stimuli suggests the presence of 



