PREFACE 



Owing to the rapid advance of Experimental Zoology, the 

 older branches of morphological study such as Comparative 

 Anatomy and Embryology, have been left in the background. 

 In order to acquire familiarity with modern methods and 

 problems, it became necessary to curtail the time allotted to 

 Morphology. As a natural consequence the laboratory guides 

 in general use in this country are more elementary than is de- 

 sirable. The result has proved in many ways unsatisfactory. 

 The student is left with only a superficial knowledge of the 

 structure, life and development of those very animals which 

 in his later studies he is going to use for experiments. 



But the high tide in Experimental Zoology has been reached 

 and passed. A general tendency to return to morphological 

 studies is manifest in recent years in the great increase in the 

 number of papers dwelling upon the anatomy of invertebrates. 

 It seems, therefore, desirable to place in the hands of the student, 

 a manual which will enable him to lay the foundation for a 

 knowledge of invertebrate anatomy. 



The usual method of teaching this subject consists in having 

 the student dissect a series of types, but while doing this he is 

 supposed to pay attention only to structures of a general char- 

 acter and to skip details. This method is open to grave criti- 

 cism. Generalization should come as the result of extended 

 observation. If we substitute generalization for observation, we 

 do the student's work for him and defeat our own end. By this 

 I do not mean to say that the student should be offered only a 

 knowledge of minute facts and left to his own resources to sift 

 the material and draw conclusions. On the contrary! The 



