opening. Study a longitudinal section of a gastrula stage. Com- 

 pare with the section of the blastula and note all differences. 

 Observe especially : 



(i). The lifting up of the floor of the segmentation cavity. 



(2). The slit-like archenteron, opening behind the dorsal lip of 

 the blastopore. 



(3). The condition of the cells in the dorsal lip itself. Draw 

 to large scale showing ectoderm, mesoderm and endoderm. 



Neural Plate. Study sections of three stages in the formation 

 of the neural plate: (i) Stage with the neural plate widely open, 

 (2) Sides of the neural plate rolling in, (3) Neural plate com- 

 pletely closed to form the neutral tube (brain and spinal cord). 



Tadpole. In cross sections of a young tadpole study and draw : 



(i ). Origin of eye-vesicle from the fore brain, and development 

 of the eye. 



(2). Cross section througn the gill region, with the heart 

 beneath. 



(3). Cross section through the ear vesicles and hind brain. 



(4). Cross section through the middle of the embryo to show 

 neural tube and crest, notochord, aorta, pronephros, somites and 

 gut. 



5. Museum Specimens. Observe in the Museum, south wing, 

 numerous preparations illustrating the development of vertebrates. 



III. COMBINATIONS OF SEXUAL AXD ASEXUAL REPRODUCTION. 



1. Metagenesis'. Alternation of asexual reproduction with 

 sexual, as in hydromedusae. 



2. Heterogeny. Alternation of monogonic reproduction with 

 amphigonic, as in fluke worms. 



IV. HEREDITY. Germinal likeness or variation as contrasted with 

 environmental. 



1. Mendelian (alternative) inheritance. Study a j nd draw 

 Museum exhibits illustrating this kind of inheritance. 



2. Give Mendelian formulas and ratios to the third filial genera- 

 tion (F 3 ) for the offspring of (a) two homozygous parents, (b) 

 two heterozygous parents, and (c) one homozygous and one hete- 

 rozygous parent. Explain sex as a mendelian character and show 

 by formulas and ratios in which of these three groups it belongs. 



3. Describe any cases of inheritance, known to you, which seem 

 to be non-Mendelian. 



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