REMARKS TO THE STUDENT Xxiii 



and texts, is made the basis for an understanding of the functions of 

 parts and of the activities of each animal as a whole. The structure of 

 a series of representative animals and the manner in which they react 

 externally and internally are examined. Upon this basis of first-hand 

 information, the discussion of more general zoological principles is 

 developed. Since it is found unsatisfactory to have students examine 

 animals in the laboratory and take no records of their observations, we 

 have recourse to note taking; and since the study of structure con- 

 sumes so large a proportion of the time, note taking is principally in 

 the form of drawings. The writing of descriptions or the tabulation 

 of experiments is also used wherever it is advisable. In most cases, 

 however, a simple figure properly labeled constitutes a better record 

 of what you have seen than any description you could write. Hence 

 drawings are the common accompaniment of laboratory work in gen- 

 eral zoology. Drawing is irksome for those who do not draw with 

 facility. Nevertheless, it is the experience of teachers that such 

 graphic representation is an effective means by which observations 

 can be recorded in work of this nature. 



There is further justification for note taking by drawings in the 

 fact that when you draw an object you are obliged to study it more 

 carefully than you can usually force yourself to do without drawing. 

 The drawing enforces more careful observation, as anyone will find if 

 he watches himself at work. If there were no other justification, this 

 alone would be sufficient reason for what is commonly required of 

 students in zoology. If you draw well, such work will be a pleasure; 

 and if you draw poorly, you will find yourself seeing more than you 

 could in any other way. 



The Technique of Laboratory Drawing. — Since the recording of 

 observations by means of figures is so extensively used as a means of 

 note taking, it will be helpful if we explain at the outset the simpler 

 principles of such representation. This may be accomplished by show- 

 ing first how lines may be dra\^-n in the two dimensions of a sheet of 

 paper to suggest the third dimension or depth of objects, and then 

 proceeding to applications in the drawing of structures such as are seen 

 in the laboratory. Referring to the accompanying Fig. 1, if we draw 

 two parallel lines, as in A, they suggest nothing more ; when the lines 

 are inclined, as in B, they suggest the convergence of the parallel lines 

 of a railroad track or similar object stretching into the distance. A 

 rectangle, C and D, may be similarly treated. A cylinder seen dirfectly 

 from the side, as in E, looks like a rectangle; when we think of it as 

 slightly tipped it looks like F and may be so drawn. Again the rec- 

 tangle dra^-n in G may be shown as though tipped backward, as in H ; 



