THE INVERTEBRATE COURSE. 103 



No text is required, although students are advised to keep at 

 hand some standard reference book, such as Parker and Has- 

 well's "Text-book of Zoology," or Lang's "Comparative Anat- 

 omy." Pratt's " Manual of Common Invertebrate Animals " is 

 constantly used with the field work. Drew's " Laboratory 

 Manual of Invertebrate Zoology," which was originally developed 

 for this course, supplemented by additional mimeographed direc- 

 tions, made out by the instructors from year to year, form the 

 guide for the laboratory work. The Laboratory library is open 

 to the students and they are constantly given references to the 

 literature, but they are more interested in studying the. animals at 

 first hand and read comparatively little. 



Typically, the subject of Invertebrate Zoology is divided on this 

 plan : 



Protozoa: Two lectures and laboratory days, followed by a 

 morning spent in collecting fresh-water protozoa from neighbor- 

 ing ponds and an afternoon's work in identifying the forms col- 

 lected. The laboratory is a compromise between the usual type 

 study and a requirement of a certain number of recognizable 

 drawings. In 1920, for example, Arc ell a was studied the first 

 half day; slides mounted a half hour before use showed active 

 movement. Amcba, Actinophrys, and Actinosphcerium were also 

 demonstrated,. Almost every one has studied Paraincciuni. but 

 by feeding the animals with hay bacteria stained with neutral red, 

 the studient, in the course of watching the feeding activity and the 

 subsequent change of the food vacuole from acid to alkaline, un- 

 consciously reviews many points of former observation, to his 

 considerable advantage. Hypotrichs are always in reserve for 

 this work. 



The second morning was occupied with Euglcna and Volvox, 

 with Ophridi it in, a green colonial vorticilid, and the gregarine, 

 Schizocystis, from Phascolosoina, in reserve. The afternoon was 

 spent on the flagellates parasitic in termites. 1 These form an 

 easily obtainable and fascinating group and it was hard to divert 



i Leidy, Jos., " Parasites of the Termites," Jour. Acad. Sci. Phila., VIII., 

 pp. 425-447 and plates, iSSi. Porter, J. F., Bull. Mits. omp. Zool., XXXIII., 

 1897. Kofoid and Swezy, Univ. of Calif. Pub. Zool., XX., 1919. 



