frequently followed program at New York University during the first aemea- 

 ter. During the second semester the students have been assigned individual 

 and original problems for investigation. 



c. Assign some of the introductory procedures to the entire class, such pro- 

 cedures as "Induction of Ovulation", "Breeding eind Care of Embryos", and 

 "Temperature and Rate of Development". Then delegate each student to 

 carry out two or three integrated procedures, with the responsibility of 

 thorough work later to be reported in full to the class. This plan de- 

 prives the student of experience in many of the techniques in experi- 

 mental embryology, but it places upon him a responsibility to the entire 

 class which often kindles the research attitude. ^ such a plan most of 

 the exercises can be attempted by an average class of about 15 students. 



A suggested sequence of exercises, which has been used at New York University, 

 is given below. The assignment is based upon a weekly class session of about k hours, 

 and supplemental time as may be required by the individual student. 



a. Induction of ovulation and artificial fertilization. 



b. Normal development: 



1. Relation of temperature to early development. 



2. Relation of osmotic pressure to early development. 

 5. The appearance of behavior patterns. 



c. Experiments with the egg: 



1. Germinal vesicle studies. 



2. Artificial parthenogenesis. 



3. Androgenesis. 



d. Experiments with the cleavage stages: 



1. The effect of unequal pressure on cleavage. 



2. The production of double embryos. 



5. The behavior of isolated embryonic cells. 



e. Experiments on the blastula and gastrula: 



1. Vital staining and morphogenetic movements. 



2. The organizer. 



f. Experiments with the neurula : 



1. Parabiosis. 



2. Regeneration. 



5- Embryonic inductions in the blastema tissue. 



g. Experiments with later stages. 



1. Wound healing. 



2. Hypophysectoiny. 



5- Limb or eye transplantations. 



This program would carry the student through about 1-^ semesters. There would 

 remain about 2 months during which the instructor could direct the students in some 

 of the more difficult techniques with either the fish or the chick embryos. 



Through the very generous help of Dr. Jane Oppenhelmer and Dr. Nelson T. Spratt, Jr. 

 the sections on fish and on chick embryos have been expanded very considerably. It is 

 believed that the traditional reluctance to use these forms is being broken down by 

 the brilliant work of investigators such as these, and the laboratory of experimental 

 embryology can no longer be limited to amphibian forms but will take in all embryos 

 from the lowest to the highest phyla. 



It would be ImpoBBlble for the author to properly acknowledge all of the help 

 that he has received in organizing this book. He has enjoyed universal and whole- 

 hearted cooperation, often entailing considerable time and effort on the part of con- 

 temporary Investigators. Where figures, graphs, or photographs have been reproduced, 



Iv 



