54 SIXTEENTH REPORT. 



LITERATURE REFERRED TO. 



Hegner, R. W., 1909a. The origin and Early History of the Germ Cells 

 in Some Chrysomelid Beetles. Jour. Morph., Vol. 20. 



1909b. The Effects of Centrifugal Force upon the Embryonic Develop- 

 ment of Some ChrA'somelid Beetles. Jour. Exp. Zool., Vol. 6. 



1911. Experiments with Chrysomehd Beetles. III. The Effects of Kill- 

 ing Parts of the Eggs of Leptinotarsa desemlineata. Biol. Bull., Vol. 20. 



EXPLANATIONS OF FIGURES. 



Fig. 1. Longitudinal section through an egg of Calligrapha multipunctata 

 which was placed in the centrifuge when fresh, rotated for 16 hours and 

 tlien killed. Three zones are visible. 6Z. =blastoderm ; g. c.=gra3^ cap; 

 7?=posterior end; t'<=vitellophag; v. z. =vesicular zone; i/=yolk. 



Fig. 2. Superficial view of an egg of Leptinotarsa decemlineata centri- 

 fuged for seven days wath the anterior end toward the center of rotation. 

 o=anterior; a6=abdomen; p=posterior; ^=thorax. 



Fig. 3. Another egg from same lot as that shown in Fig 2. 



Fig. 4. As in Fig. 2 except centrifuged Tvath the posterior end toward 

 the center of rotation. 



Fig. 5. Ventral view of an embryo of Leptinotarsa decemlineata 72 hours 

 old. ab =abdomen; h =heacl; t =thorax. 



Fig. 6. Right side of an embryo of Leptinotarsa decemlineata 48 hours 

 old, showing tail-fold on dorsal surface. a=antenna; w?=mandible; m^ = 

 first maxilla; w- = second maxilla; ^'-^^ = thoracic appendages; tj= tail- 

 fold. 



Fig. 7. Longitudinal section through fresh egg of Calligrapha bigshyana. 

 gfCf/ = germ-track-determinants; gn = germ nuclei fusing; /c/iW = Keimhaut- 

 blastem; p=posterior; i'm=vitelhne membrane; 7/=yolk. 



Fig. 8. As in Fig. 7 except egg 14 hours old. Pbln =preblastodermic 

 nuclei; ?;i =vitellophag. Other lettering as in Fig. 7. 



Fig. 9. Longitudinal section through egg of Leptinotarsa decemlineata 24 

 hours old showing fully formed blastoderm {bl) and primordial germ cells 



