272 BERTRAM G. SMITH. 



EXPLANATION OF PLATE II 

 Cryptobranchus allegheniensis. 



FIG. 5. Horizontal section of a fertilized egg showing the germ-nuclei preparing 

 for the first cleavage mitosis. The germ-nucleus shown at the right is in a slightly 

 more advanced phase than the other. A portion of each nucleus is left in an 

 adjacent section. Bichromate-acetic-formalin fixation; stained with borax-car- 

 mine Lyons-blue picric-acid. X 400. 



v* 



FIG. 6. Horizontal section of an egg killed twenty-two and one half hours 



after fertilization, showing the germ-nuclei preparing for the first cleavage mitosis. 

 The germ-nucleus shown at the right is in a more advanced phase than the other. 

 About half of each nucleus is left in an adjacent section. Bichromate-acetic- 

 formalin fixation; stained with borax-carmine Lyons-blue picric-acid. X 400. 



FIG. 7. Horizontal section through the first cleavage spindle (late prophase). 

 The chromosomes are segregated into two groups, of maternal and paternal origin 

 respectively. A very small portion of each group of chromosomes is left in each 

 of the adjacent sections. Bichromate-acetic-formalin fixation; stained with iron- 

 ha?matoxylin. X 400. 



FIG. 8. Horizontal section of an egg killed twenty-six hours after fertilization , 

 showing a late stage (early telophase) of the first nuclear division. In the distribu- 

 tion of chromatin to the daughter-nuclei, the segregation of maternal and paternal 

 chromatin is maintained. A very small portion of the chromatin of each daughter- 

 nucleus is left in an adjacent section. Bichromate-acetic-formalin fixation; stained 

 with borax-carmine Lyons-blue picric acid. X 400. 



