MOVEMENT 



With these the free movement of the unicellular pro- 

 tozoon is farther advanced through the formation of 

 permanent hairlike processes (long single lashes in the 

 flagellata, and a number of short lashes in the ciliata) 

 on the cell-surface and the movement of these jby con- 

 traction and expansion, like the limbs, tentacles, and 

 bones of the higher animals. The apparent spontaneity 

 and various modulation in the ever-changing move- 

 ments of these cell-feet is, in many of the infusoria, 

 so like the autonomous voluntary movements in the 

 metazoa that several experts on the infusoria have been 

 moved on this account to ascribe individual (and even 

 conscious) souls to them. Hence the difference be- 

 tween the various kinds of living movement is already 

 very considerable before we leave the kingdom of the 

 protists. On the one hand, the lowest monera (chro- 

 macea) join on directly to inorganic phenomena. On 

 the other hand, the highly differentiated infusoria 

 (ciliata) show so great a resemblance to the higher 

 animals in their differentiated and autonomous move- 

 ments that they have been credited with the possession 

 of ' ' free-will . ' ' There is no such thing as a sharp division . 

 In a large section of the higher protozoa differentiated 

 organs of movement are developed, which may be com- 

 pared to the muscles of the metazoa. In the cytoplasm 

 threadlike, contractile structures are formed, and these 

 have, like the muscular fibres of the metazoa, the power 

 to contract and expand again in definite directions. 

 These myophsena or myonema form, in many of the 

 infusoria, both ciliata and flagellata, a special thin 

 layer of parallel or crossed fibres underneath the exo- 

 plasm or the hyaline skin-layer of the cell. The metab- 

 olic body of the infusorium may be altered in various 

 ways by the autonomous contraction of these. Special 

 instances of these myophaena are the myophrisca of the 

 acantharia — contractile threads which surround the 



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