OF MICRO-ORGANISMS. 17 



and the Spirostomes the fibrillous striae are in intimate 

 connection with the basilar extremity of the vijpratile 

 cilia. In the Vorticellae one can clearly see the fibrils 

 converge toward the axis of the style, the contractile 

 element of which they constitute. 



We shall not leave the study of the motor organs 

 without saying a word about the rhythmical movements 

 which can be seen in the contractile vesicle of the 

 Micro-organisms, vegetable as well as animal. This 

 vesicle is a small cavity which is dug into the proto- 

 plasm, and which alternately increases and diminishes 

 its capacity. Scientists by no means agree as to its ex- 

 act function; Biitschli and Stein consider it to be a 

 secretive apparatus. Its pulsations are very regular. 

 Their number is constant in every species. In the 

 chilodon cucullulus, a pulsation occurs every two sec- 

 onds; in the Crytochium nigricans, every three sec- 

 onds; in the Vorticellae, every eight seconds; in the 

 Eiiplotes, every twenty-eight seconds; in the Acineria 

 incurvata, every six minutes; Rossbach, whose curi- 

 ous experiments with the vibratile cilia and the cirri 

 we have already cited, has made analogous experi- 

 ments with the contractile vesicles. He observed es- 

 pecially that, under the action of alkaloids, the con- 

 tractile vesicle ceased pulsating in diastole, and di- 

 lated enormously; but poisonous agents do not act 

 all at once on the movements of the vesicle; they begin 

 by paralyzing the larger cilia, which are under the in- 

 fluence of the will. The movements of the vesicle, 

 like those of the small cilia, persist for a much longer 

 time. M. E. Maupas has seen Paramecia, killed by 

 a discharge of trichocysts, become completely immo- 

 bile, with their vibratile cilia inert and rigid, 

 while the contractile vesicle continued to pulsate 



