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FISH FOR EXPERIMENTATION 











Semi -diagrammatic sketches of preserved Fundulus embryos to show the comparative stages of organ formation. 

 Made with the assistance of a comera-lucida. 



1. Twenty-eight-hour-old embryo in which the embr>'onic shield is differentiating and invagination has begun. 



2. Thirty-six-hour-old embryo in which the embryonic axis has begun to be recognizable. 



3. Forty-cight-hour-old embryo, just before the formation of the somites. 



4. Ten-somite embryo. Note the beginning of the optic cups and auditory structures. 



5. Fifteen-somite embryo. Considerable change has occurred in the organization of the brain and sense organs. 



6. Twenty-five somite embryo, eighty hours of age. Note the increase in size as well qs the degree of 

 differentiation. 



Camera-lucida drawings of sections through the optic vesicles of Fundulus embryos. 



7. Embryo in one-somite stage. 



8. Embryo in seven-somite stage. 



9. Embryo in ten-somite stage. Note the flattened optic vesicles and lens anlagen. 



10. Embryo in fifteen-somite stage. The optic cups are nearly complete and the lenses are developing. 

 I 1. Embryo in twenty-five-somite stage. The lenses are completely separated from the ectoderm. 



(From Jones 1939: Trans. Am. Microscopical Soc. 58!1) 



