All the drawings were made with a camera, with a 2 mm. Zeiss apochromatic 

 objective, and a No. 6 compensating ocular, unless otherwise stated. 



PLATE 1 



EXPLANATION OF FIGURES 



1 to 4 Normal Fertilization. 



1 Attachment of the sperm ; 55 minutes after insemination. 



2 Penetration of the sperm head; 60 minutes after insemination. 



3 Telophase of the second maturation division, and approach of the sperm 

 nucleus; 65 minutes after insemination. 



4 Just before the fusion of the germ nuclei; 90 minutes after insemination. 



5 to 9 Fertilization of normal eggs by radiated sperm. 



5 Penetration of the sperm head, showing absence of the fertilization cone; 

 60 minutes after insemination. 



6 Development of the egg nucleus, and failure of the sperm nucleus to enter; 

 115 minutes after insemination. 



7 Gradual disappearance of the sperm aster; 105 minutes after insemination. 



8 Total disappearance of the sperm aster. The sperm nucleus has divided 

 into many vesicles; 115 minutes after insemination. 



9 to 29 Fertilization of the radiated eggs by normal sperm. 



9 Polyspermy. This egg has failed to extrude the alveolar layer. 2 mm. 

 apochr. and No. eyepiece. 



10 Detail of the same; 70 minutes after insemination. 



11 Formation after the first maturation figure without astral sj^stem. 



12 Same, with spindle but no asters; 45 minutes after insemination. 



13 Same. The chromatin is segmented, but is splitting longitudinally 45; 

 minutes after insemination. 



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