202 PROCEEDINGS OP THE AMERICAN ACADEMT. 



EXPLANATION OF PLATE II. 



Neritina after Blochmann ('81). 



The arrows, indicating the derivation of cells, and the nomenclature placed 

 within the limits of the figures are mine ; the rest of the nomenclature is repro- 

 duced from Blochmann's figures. It is to be observed that his lettering, a, b, c, d, 

 is from right to left, whereas my own is that generally accepted, — from left to 

 right. The explanation of these figures is taken from Blochmann, and the term 

 '' generation " is used in the sense in which he has employed it. 



Figure 7. Taf. VII. Fig. 45. " Formation of the cells of the sixth generation, 



"l 1 V c i ! ^l 1 - Rhl, polar globules." 

 " 8. Taf. VII. Fig. 46. "Formation of the cells of the seventh and 



eighth generations, a 3 b 3 c 3 d 3 and a 2 ' b 2 l c 2 l d. 2 l ." 

 " 9. Taf. VII. Fig. 47. "The same stage in profile." 

 " 10. Taf. VII. Fig. 48. " Completed twenty-four-cell stage." The long 



arrows, indicating a change of interpretation, are mine. 

 " 11. Taf. VII. Fig. 50. " Twenty-eight-cell stage ; a 2 u b 2 u c„» J 2 ", cells 



of the ninth generation." 

 " 12. Taf. VII. Fig. 51. " Thirty-six-cell stage ; vz derived from a. 2 u , vz x 



from c 2 i [my 6 7-3 ], d 2 lu from d 2 l , a z l from a 3 , etc. 



