2 ELEMENTS OF COMPARATIVE ZOOLOGY. 



previous dissections, and are intended to bring out clearly 

 in the student's mind the essential points of resemblance 

 and of difference in the forms studied, and the bearings of 

 the facts discovered. Laboratory work trains the powers 

 of observation; the answering of the questions leads to a 

 systematization of knowledge and an exercise of the rea- 

 soning powers. The value of nature studies lies more in 

 the training of the mind than in the acquisition of facts. 

 Hence each pupil should be required to hand in answers to 

 these questions, and to make these answers as detailed 

 as possible. 



Following each laboratory section is a general account of 

 allied forms and a statement of the principal character- 

 istics of the group, thus giving a completeness to the 

 knowledge which otherwise would be utterly lacking. In 

 these general statements there are frequent references to 

 the sections where the student has worked out the point 

 for himself. The work throughout is based upon the in- 

 ductive method, and finally the animal kingdom is shown 

 as a whole. 



APPAKATUS NECESSARY. 



The room used for laboratory purposes should be well 

 lighted and should be furnished with running water. 

 There should be receptacles for waste, and the students 

 should be made to keep everything clean. 



The tables for laboratory work should be low (not over 

 29 inches from the floor), and should afford each student 

 at least six square feet of surface. It is best that there 

 should be no varnish upon them, as this makes trouble 

 when alcohol is spilled. 



Each student should have the following instruments : A 

 scalpel ; a pair of scissors j a pair of forceps ; two dissecting- 



