680 BEPORT OF COMMISSIONER OF FISH AND FISHERIES. [124] 



EXPLANATION OF PLATE U. 



Fig. 9. CodV .-^g eight hours after impregnation, the genuinal disk undergoing di- 

 vision into two halves, viewed from below; oblique illumination, x 30. 



FiG. 10. Gcniiinal disk of cod's egg nine and a half hours after impregnation, show- 

 ing the completion of the second cleavage through its longest diameter 

 dividing each of the first two cells of the preceding figure, resulting in 

 four new ones. The nuclei and granular contents of the cells shine 

 through in this and the foregoing figure. Oblique illumination, x 30. 



FlO. 11. Cod's egg twenty-three hours after impregnation ; the disk is shown at lower 

 side of the yelk, viewed from the side, x 30. 



FlQ. 12. The germinal disk of the preceding, viewed from below, showing fourteen 

 cells, the products of further cleavages, x 30. 



Fig. 13. Cod's egg forty-five and a half hours after impregnation, in optic section, 

 showing still further progress in the cleavage of the disk, as a result of 

 which about three superimposed layers of cells have been formed, x 50. 



Flo. 14. Cod's egg four days after imj»regnatiou, showing a still further advance in 

 cleavage, through which a multicellular disk (morula) has arisen, which 

 IB very strongly convex on the inner side towards the yelk, x 50. 



