EXPLANATION OF PLATE I. 



Unless otherwise stated all the figures on this and succeeding plates were 

 drawn from eggs or embryos of Calligrapha multipunctata. Lines drawn 

 through figures on this plate indicate where sections were made, and refer by 

 number to more highly magnified illustrations on the following plates. The 

 germ-cells (pole-cells) are represented by small rings. All are magnified 35 

 diameters. 



Stage A. The pole-cell nuclei are protruding at posterior end. No blasto- 

 derm-cell nuclei have yet reached the surface. 



Stage B. All the pole-cells (64) lie in a group outside of the egg at the 

 posterior end. 



Stage C. Ventral surface of egg. The lateral folds of the ventral plate have 

 appeared. 



Stage D. View of ventral surface. The group of pole-cells has been carried 

 part way up on the ventral surface. 



Stage E. Ventral view of egg. Pole-cells lie in posterior depression of ven- 

 tral groove. First appearance of germ-band. 



Stage F. Ventral groove narrower than in Stage E. Pole-cells partly covered 

 by lateral folds. 



Stage O. Lateral view of same egg as in Stage F. Dotted line shows depth 

 or ventral groove. Pole-cells lie at entrance to pole-cell canal. 



Stage H. Lateral view. Amnioserosal fold partly covers germ-band. Pole- 

 cells lie at end of posterior amniotic cavity ; a few have passed through the 

 pole-cell canal. 



Stage J. Germ-band, in lateral view, almost covered by amnioserosal fold. 

 More pole-cells are inside of germ-band than in younger stage (H). 



Stage K. View of lateral surface of segmented germ-band. Nearly all of 

 the pole-cells are now inside the embryo. 



Stage L. Lateral view after appearance of appendages. Tail-fold shorter 

 than in preceding stage (K). Germ-cells have separated to form a group on 

 either side of tail-fold in last two abdominal segments. 



Stage M. Upper figure represents ventral surface of embryo ; lower figure, 

 the posterior portion on dorsal surface. Tail-fold is short and broad. Germ- 

 cells are closer to one another than in Stage L. 



Stage N. Upper figure represents ventral surface of embryo ; lower figure, 

 the tail-fold on the dorsal surface. Germ-cells form two definite compact 

 germ-glands. 



Stage O. Ventral view of embryo. End of tail-fold now coincident with 

 posterior pole of egg. Germ-glands lie near ventral surface on either side of 

 median line. 



