iv PREFACE 



sion of the teacher. The course has been arranged so that any 

 of these methods may be adopted. 



Many teachers prefer to begin a laboratory course in general 

 zoology with a frog or a fish, as convenient and relatively simple 

 forms to use in introducing a class to laboratory methods of study, 

 and this is one of the reasons for the expansion of this work by 

 the introduction of these dissections into it. 



While the comparative feature runs through the dissections in 

 this course, each is complete in itself and does not depend upon 

 any others. The teacher is thus enabled to give his class such 

 dissections as he wishes and is not compelled to adopt the entire 

 series to have his course complete. He can also reverse the order 

 of the studies, if it suits his purpose better, beginning with the 

 Protozoa and working upward to the higher groups. 



An important feature of the plan of the course has been to give 

 the student such practical directions that he can go on with his 

 work intelligently and profitably without having an instructor 

 constantly at his elbow. Far too much of the time of the average 

 youthful student is often wasted in the laboratory because the 

 instructor does not happen to be at hand at critical times to direct 

 his work. The student will often do the work wrong in conse- 

 quence, or perhaps he will not do anything at all ; in either case 

 his time is wasted and perhaps his material spoiled. 



In most of the dissections the directions are so arranged that 

 the student can complete the study with a single specimen, and 

 in the longer dissections with two specimens, or at most three, 

 and the order in which the different systems of organs are taken 

 up in each dissection is made dependent upon this feature. The 

 necessity of practicing economy of material is thus inculcated, 

 and the habit is acquired of studying and handling each speci- 

 men with care and judgment. 



H. S. PRATT 



Haverford, Pennsylvania 



