' 1896.) Embryology. 773 
7. The second and fourth grooves start from the periphery and move 
toward the pole. 
8. The blastomeres are more rounded and the segmentation furrows 
are deeper than those in most frog’s eggs. 
9. The development is very rapid ; gastrulation begins within twelve 
hours, and the tadpole escapes from the egg during the second or third 
day.— Cuarues B. WILson. 
ExPLANATION OF PLATE I. 
All figures drawn with Zeiss Camera x 16 diam. 
Figs. 1-4. Successive stages i in pees of living egg at intervals of 
3 mins., 3 mins., 2 min 
Figs. 5,6. Stages in cleavane of ee living egg. 
Figs. 7-9. Stages in ine of third living egg—intervals, 2 mins., 
4 mins. 
Figs. 10-15. Stages in ie of fourth living egg—intervals, 2, 6, 
3, 4, and 5 min 
Figs. 16-18. Stages in second oe: of pan egg. 
Figs. 19, 20. Variations in second cleavag 
Fig. 21, Eight-cell stage of first egg. 
Figs. 22-24. Stages in third cleavage of second egg. 
Figs. 25-27. Variations in sixteen-cell stage. 
EXPLANATION oF PLATE II. 
All figures drawn with Zeiss Camera. 
Figs. 28-30. First cleavage under higher magnification to show 
rounded blastomeres. 
Figs. 31, 32. Beginning of first cleavage, showing radiating wrinkles 
at pigmented pole. 
Figs. 33-35. Variations in wrinkles on the first furrow. 
Fig. 36. View of an egg during the fourth cleavage. 
Fig. 37. The same egg four minutes later. 
Fig. 38. Fusion and partial disappearance of the first groove. 
Fig. 39. Horizontal section of an egg during the first segmenta- 
tion, taken at the level of the bottom of the furrow. 
Nuclei added from the fourth section below this. 
Fig. 40. A portion of the same furrow about half way between 
its bottom and the surface of the egg, more highly 
magnified. 
