MOVKMKNTS, ETC., OF PRKSII-WATKIJ I'l.AXAElANS. G85 



far ;is iiun'linnisni is ooiict'Tiiod. Cut ])ioc{'s, in wliicli tlic 



nurinal ineclianisin for tlic rio'litiny reaction lias been 



destroyed, rig-ht themselves in various ways, thus showing a 

 sort of regulation in reactions. 



lA'^. El ec trot axis. 



In view of the sliarp and precise reactions of ]^l;inarians to 

 other stinnili, it was thought tliat they would furnish excellent 

 oljjects for tlie study of electnjtaxis, Init nnfortnnntely this is 

 not the case. Their reactions to the constant current are nf)t 

 clear-cnt, since the specimens become wholly or partially 

 paralysed in a very short time after the current begins to 

 act, and as a consequence the reactions become feeble and in- 

 distinct. For tho sake of completeness, however, and since 

 some facts of importance are brought out, the experiments on 

 this subject will be briefly reported. 



a. Methods. — The following methods were used: — The 

 constant current used was obtained from the general lighting 

 circuit of the University, and reduced to the proper intensity 

 by interposed resistance. This apjiaratus for getting the 

 current I have described fully elsewhere (: 00, : 01), so that 

 it need not detain us here. In the circuit a rheostat was 

 inserted for regulating tlie strength of the current. Ordinary 

 unpolarisable brush electrodes were used. The specimens 

 were placed either in a trough with clay ends, to serve as 

 poles, and with paraffin sides of 5 mm. depth, or else on a 

 slide under a cover supported by several layers of moistened 

 filter-paper. These filter-paper ends then serve as the poles 

 of the preparation, the brushes of the electrodes being laid 

 upon them. The layer of water in which the specimens were 

 in this sort of a preparation was approximately 2'5 mm. in 

 thickness. Identical results were obtained by both the trough 

 and the filter-paper method, but since tho latter is the lu^ater 

 and generally more satisfactory method, it was used almost 

 entirely in preference to the trough. 



h. Results. — The typical result of the action of the 

 current on specimens in such a position that the long axis of 



VOL. 46, PAKT 4. NEW SERIES. Y Y 



