534 



SCIENCE. 



[N. S. Vol. V. No. 118. 



limits of the paper will permit. I cannot 

 refrain from calling attention to the clear- 

 ness with which the students of biology 

 learn that the omission of a single step in 

 the treatment of tissue, or even the slight- 

 est variation from a specified course of pro- 

 cedure, will invariably modify or invalidate 

 the results attained. This lesson has great 

 educative value in impressing upon the 

 mind the consequences of variation from 

 truth in all procedures, demonstrations or 

 speculations. 



Having given so large a portion of my 

 time to the discussion of pedagogical prin- 

 ciples, I hasten to the suggestion of modes 

 and measures to make this scheme effective 

 and operative. 



Whenever the teacher is prepared by 

 previous training to present the subject of 

 comparative zoology, my experience of 21 

 years as teacher of biology has convinced 

 me that the best results can be secured with 

 students of high-school grade by beginning 

 with the simplest unicellular organisms and 

 proceeding to the more complex. The 

 pupil who has a clear, definite knowledge 

 of an amoeba is prepared to comprehend 

 the structure of complex forms, and with 

 this knowledge he cannot fail to grasp the 

 secret of animal morphology. When some 

 of the more complex forms are studied 

 minutely the problem presents two phases: 

 shall one form be studied minutely, and 

 shall the available time be given to the 

 study of a few types, or shall the study of a 

 single type be less exhaustive and a larger 

 number of types be examined ? 



I am satisfied that I have secured the 

 best results by the study of many types, 

 for comparative study rendered the knowl- 

 edge of each type apperceptive, and the en- 

 larged circle of experience gave the enlarged 

 interest based upon enlarged knowledge 

 which cannot exist with a restricted con- 

 tent to the concept. Thus in the study of 

 the ccelenterata we examined not only a 



simple hydra, but studied one or more com- 

 plex marine forms, some from actual alco- 

 holic specimens, others by means of charts 

 and diagrams. Polyp, anemone (Metrid- 

 ium), jelly-fish (Aurelia), holothurian 

 (pentacta), sea-urchin (Toxopneustes) , 

 sand-dollar (Echinarachnius), brittle-star 

 (Ophiopolis), not only aid in the formation 

 of a correct concept of the Coelenterate 

 type, bnt the knowledge gained from the 

 study of each makes the study of the 

 others more significant. I do not hesitate 

 to af&rm that the examination of half a 

 dozen type specimens carefully dissected by 

 the teacher will give a clearer and better 

 knowledge of the type in one class period 

 than a week's study of a single specimen 

 by an untrained pupil who is vaguely work- 

 ing in the dai-k, with scalpel and specimen, 

 acquiring habits of wastefulness and slov- 

 enly generalizations. Where time and ap- 

 pliances will permit, more individual work 

 is desirable; the best and the most econom- 

 ical mode known to the writer is that in- 

 augurated and followed by Dr. B. G. Wilder, 

 of Cornell University, in what he has hap- 

 pily named Practicums.* But quantity is 

 essential to quality, a principle true in 

 every line of research. Something more 

 than effort is demanded. 



After careful training to observation of 

 the significance of homologues it is of great 

 value to let each pupil trace a type struc- 

 ture, e. jr., the distribution of a spinal nerve 

 in two or more types, as in the cat, dog, 

 rabbit, and learn the significance of per- 

 sistence of type-forms. No exercise of mind 

 can be made more conducive to that judicial 

 habit which is essential in everj' department 

 of life and yet is so rare. 



From a utilitarian standpoint all this 

 knowledge of animal structure and func- 

 tion becomes the basis of the study of 



* Outline directions for these Practicums can be 

 obtained by addressing B. G. Wilder, Ithaca, N. Y. 

 Price, $1.00. 



