CHAPTER XXIX 



EXERCISES IN COMPARATIVE PHYSIOLOGY, MORPHOLOGY, AND 



ECOLOGY 



522. Now that the student has studied in some detail the 

 work which even the simplest organisms must perform, the 

 organs by means of which this necessary work is done in some 

 of the principal types, and the relations which animals assume 

 to each other and to the environment in general, it is desirable 

 that he should bring these facts into such relations that they 

 may be compared. The likenesses, the unlikenesses, and the 

 progressive differentiation are thus brought into clear relief. 

 The following outline exercises are intended to guide the stu- 

 dent in this task. They are by no means exhaustive, but will 

 suggest the principal points most essential to such a resume. 

 The laboratory notes, the textbook, and all the reference books 

 at his command, should be used by the student. The student 

 should be able to cite his authority for all important statements 

 not his own, and, if possible, corroborate by reference to more 

 than one authority. Tables with parallel columns such as 

 those on pages 343 and 346 furnish an economical and other- 

 wise satisfactory mode of displaying the results of these studies. 



I. Fundamental Form (Promorphology). Indicate for each 

 of the important phyla, or for chosen representatives of them, 

 the following matters of general form: kind of symmetry rep- 

 resented and the perfection of its development; the degree and 

 character of segmentation; the position, number, character, 

 and arrangement of the appendages; the external and the in- 

 ternal evidences of cephalization ; the relation of the principal 

 organs of the animal to the horizontal and vertical planes. 



II. Physiology and Morphology. Compare the mode of 

 performing the following functions and the organs used therein, 

 in all the principal animal phyla. 



1. The capture of food: the method; the organs devoted to 

 it ; and the relation of these to the nature of the food used. 



2. Digestion; physical and chemical. 



520 



