REMARKS TO INSTRUCTORS . XV 



4. Reproduction and development in vertebrates are discussed 

 with emphasis on the cell movements and early localiza- 

 tions of organ-system primordia. The frog as a laboratory 

 form is compared with other chordates in order to bring 

 out the fundamental sequence of events and its various 

 modifications. 



II. Heredity and Variation, with emphasis on the experimental and 

 theoretical aspects of modern genetics. No laboratory work is 

 given in this topic. 



III. The Structure and Activities of Representative Invertebrate 

 Animals. 



1. The Protozoa, as physiologically balanced cells or unicellular 



organisms, are compared with the vertebrate as a unit, as 

 well as with its individual specialized cells. The require- 

 ments for the maintenance of protoplasm are further illus- 

 trated as in all the forms studied. 



2. Origin of somatic cells and their increasing specialization and 



organization into the typical body-plans are traced 

 through protozoan colonies, the hydra, earthworm, and 

 other invertebrates. Increasing specialization of the sensory- 

 neuro-muscular mechanism in multicellular, free-living 

 animals is pointed out. Variations in organ-systems and 

 similarities in fundamental functions are emphasized in 

 comparison with the vertebrates. Dissection and micro- 

 scopic study of selected forms constitute the laboratory 

 program. 



3. Parasitism, symbiosis, colony formation, and society organi- 



zation, as well as other animal interrelations, are consid- 

 ered in connection with the various groups. 



4. General ecological principles are illustrated wherever 



possible. 



5. The economic importance of other animals to man is dis- 



cussed particularly in connection with the Mollusca and 

 Arthropoda. 



IV. The Classification and History of Animals. 



1. The principles of classification are considered in general and 



illustrated for a phylum by the animal studied in the 

 laboratory, as well as by related demonstration specimens. 



2. The evidence for organic evolution as the manner of origin 



of the numerous types of present-day animals is presented, 



