Xiv REMARKS TO INSTRUCTORS 



we began using Parker and Parker's text, the frog, the Protozoa, the 

 hydra, and the other animals included were studied as representatives 

 of biological principles and not of animal phyla. With the develop- 

 ments in zoology of recent years, increasing attention has been given 

 in the lecture room to the physiological, developmental, and genetic 

 aspects of the science. Various textbooks were used, but the program 

 of the course was always based upon the conviction, first, that we 

 should teach principles, not phyla, and second, that the best way to 

 teach principles is by the intensive study of a limited number of ani- 

 mals suited to illustrate them, followed by demonstrations of the ap- 

 plication of these principles in other cases. In the history of zoological 

 investigation it appears that the best understanding of principles has 

 usually been gained not by the initial study of many cases, but by the 

 intensive study of a single favorable example with subsequent exten- 

 sion and verification in other instances. Boveri with Ascaris, Morgan 

 with Drosophila, and Woodruff with Paramecium are illustrations. 

 We believe it is so in the teaching of students. Have them study the 

 one case as thoroughly as time allows, and then show them how to 

 apply the principles over a wide range of cases. If too many cases 

 are presented and the comparisons made at the outset, they cannot 

 see the forest for the trees. When they have studied one tree inten- 

 sively they can understand that different kinds of trees present various 

 modifications and that a forest is nothing but a collection of trees. 



To illustrate specifically, the course in general zoology as con- 

 ducted at the University of Missouri and now outlined by the "Text- 

 book of General Zoology," which these Directions are designed to 

 accompany, includes the following topics: 



I. The Structure and Activities of Vertebrate Animals. 



1. Vertebrate organ -systems are studied by dissection and a 



limited number of physiological experiments. The com- 

 plex multicellular animal is analyzed as a physiologically 

 balanced unit made up of specialized, coordinated systems. 

 Function is explained in terms of the requirements for 

 protoplasmic maintenance. 



2. Cell specialization is illustrated by the histology of verte- 



brates. 



3. Special activities of cells during cell division and gameto- 



genesis are presented with special reference to the behavior 

 of the chromosomes in preparation for the study of hered- 

 ity and variation. 



