so TIIK AMKKUWN MoN'rill.V 1 Mar.li, 



Hardening. — Inihod in <;iim as clcscrilird. 



Sections. — Hv niicndoim- ; st-ctidns to remain in water 20 

 niinntt's. 



Staining. Hv lianiatoxylin and cosine. 



Preservation - -In dannnar. 



[M. Boiicval docs not like Canada lialsam as a in<)iintin<j 

 nu-dium. pieferrinj; dammar. Hereafter, wlienever the word 

 ••balsam" is used it will be nndcrstood that tiie author means 

 dammar, althonjjh either halsam or dammai mav l>e employed, as 

 the readci- may prefer.] 



f 7'c> hr conftHurd j 



TIh' ("oiitractih' Vosidoof Paramocluiii. 



i;v ALIIHRT SCllNKIDMR. M. D.. 



MINNRAPOLIS, MINS. 



The functions of the contractile vesicle in jjroto/oons are but 

 little un«lerstood, in spite of the fact that carefid work has been 

 done on them. Doubtless the question will not be fullv solved 

 for some time. The cause of the dirticulty is pr()bal)ly to be 

 found in the delicate chemical reactions involved. The assertions 

 of earlier /o<)lo<)jists were misleading. Some described the con- 

 tractile vesicle as a sort of " water pump." others as a " heart." 

 Stein mentions the •• neaily pure water " found in the contractile 

 vesicles, and how •.' it is forcetl to the exterior throuj^h an opening; 

 or openings in the cell wall." The comparison to a "■ heart" is 

 far fetched and meaningless. JJiitchli (iSSi and 'S2) seems to 

 incline towards Stein's view. One gains but little satisfaction 

 from the present literature on the subject. Though I am not 

 now able to make anv conclusive statements, yet I hope to con- 

 tribute something towards solving the mysterv. I have made a 

 special study of it. 



I used a \-\n. Zeiss objective with \\. ocular. In order to 

 reduce the activity of the organism, I used C()^ and chloro- 

 form vapor. This was rather unsatisfactory, owing to the care re- 

 quired in admitting the reagent. The sliglUest excess would soon 

 (iestroy life. Besides, the conditions were far from normal. A 

 far better method is that suggested bv Professor H. F. Nachtrieb, 

 of using a solution of cherrv gum just thick enough to render 

 the specimeiTi comparatively inactive. Hy this method I could 

 keep them alive for hours and study both their movements and 

 the action of the contractile vesicle. The mechanical parts of the 

 experiments I need not describe, as they were very simple. 



As is well known, Parameciutn anrelia has two contractile 

 vesicles located in the ectosarc opposite the ventral side. As a 

 rule, they contract alternately with great regularity. The 

 average time required f<^r a complete pidsation is about one 



