4 DAVENPORT ACADEMY OF SCIENCES. 



» 



the shrinking effect of the glycerine by a judicious use of acetic 



acid. 



Glycerine-jelly also may be used as a mounting medium, having 

 some advantages over glycerine. Some naked Protozoa of consid- 

 erable consistency may be fixed in a drop of water, then allow- 

 ing the water to evaporate, the organisnjs adhering to the slide 

 may be stained, dehydrated, cleared and mounted in accord with 

 the usual histological methods. 



As a general fixing agent the fumes of osmic acid have proved 

 very satisfactory. 



In the preparation of this paper the microscopic work, for the 

 most part, was done in the zoological laboratory of the State Uni- 

 versity of Iowa. 



To Prof. Nutting, at whose suggestion this report was initiated, 

 I am exceedingly grateful not only for his having placed at my 

 disposal the best facilities afforded by the department of Zoology, 

 but also for direction and encouragement in the pursuance of the 

 work. 



Profs. Wickham and Houser have also rendered assistance by 

 way of valuable suggestions. 



The classification employed in this paper is a combination 

 derived from several sources, following quite closely, however, the 

 .scheme of Calkins in his volume, "The Protozoa," this being, it 

 seems to me, a convenient system of grouping. No attempt is 

 made to give a complete table of classification of Protozoa but, for 

 the most part, only those orders and families are included, types 

 of which have been observed or are likely to occur in the waters 

 of this state. 



