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THE AMEBIC AN NATURALIST [Vol. LI 



uals, would tend to be transmitted to the entire colony by 

 the mere contact of their bodies. 



The same sort of synchronous movement may sometimes 

 be noted in the reactions of the leaves and leaflets of the 

 sensitive plant {Mimosa pudica). A sudden shock may 

 cause every leaf of the plant to react synchronously. 

 Sometimes, when the stimulus is applied only to one or 

 two pairs of the basal leaflets, the closing of these and 

 their contact with those beneath them produce a pro- 

 gressive closing movement in all the pairs of leaflets 

 until the terminal ones are reached. In this instance we 

 have a progressive transmission of stimuli quite similar 

 to the transmission of certain automatic reactions which 

 sometimes take place in groups of insects, birds, or ani- 

 mals. 



In other instances the reaction to a certain stimulus may 

 involve several similar, instinctive movements producing 

 the simplest form of synchronic rhythm. One interesting 

 instance of this sort of synchronous action has been ad- 

 duced by H. H. Newman, in Science, N. S., for January 

 12, 1917. Newman found that an enormous colony of 

 *'harvestmen," of the genus Liohunum, resting beneath 

 an overhanging rock, when disturbed began a rhythmic 

 body movement, raising their bodies up and down at a 

 rate of about three times a second, for a brief period. If 

 the stimulus was set up in a few individuals of the colony, 

 the synchronous body movements spread rapidly over the 

 entire colony. After a time it was found that the reactions 

 became weaker and finally ceased. In this instance it ap- 

 pears that there was a secondary transmission of the 

 stimuli from individual to individual by means of their 

 closely interlocked legs. Tlie wi'iter has noted a similar 

 behavior among the individii.ils of ccit.-iiii caterpillars 

 which were arranged close to^ci iu-i- on ;i t wig. These 

 caterpillars, when resting, Imd tlic linl.it of k('<>piim- the 

 anterior portion of their bodio iih-imI in ihc ;iir. If the 

 colony was disturbed, each iiidi \ i< hial hrii-.-ni ;i >> n('hronous 

 swinging of the free portion ihc hody t'l'oni Ado to side, 

 violently, for a brief period. The in imary -stimulus could 

 affect all the caterpillars of a gfou]), oi- a socoiidary trans- 



