GENERAL BIOLOGY 



In the latter the blastopore is circular in outline and the yolk plug 

 fills up its opening. Study a longitudinal section of a gastrula stage. 

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

 Observe especially: 



a. The lifting up of the floor of the segmentation cavity. 



b. The slit-like archenteron, opening behind the dorsal lip of 

 the blastopore. 



c. The condition of the cells in the dorsal lip itself. 



Draw to large scale showing ectodern, mesoderm and endoderm. 



IV. Neural Plate. Study sections of three stages in the forma- 

 tion of the neural plate: (i) Stage with the neural plate widely 

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

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



Draw. 



V. Tadpole. In cross sections of a young tadpole study and 

 draw : 



1. Origin of eye-vesicle from the fore brain, and development 

 of the eye. 



2. Cross section through the ear vesicles and hind brain, show- 

 ing the gill region, with the heart beneath. 



3. Cross section through the middle of the embryo to show 

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

 gut. 



Draw and label. 



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

 numerous preparations illustrating the development of vertebrates. 



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