294 CLA YPOLE. 
EXPLANATION OF PLATE XXII. 
Blastoderm Formation. 
Fic. 30. Section through unsegmented egg. .2., protoplasmic island in which 
female pronucleus is present; ¢.f., central mass of protoplasm; *., radial proto- 
plasmic strands; other letters as before. Borax carmine. Obj. 4, oc. 6. 
Fic. 31. Section through line Z-Z in Fig. 21. 01, blastomere; ¢., egg 
membrane; v., vitelline membrane. Iron haematoxylin and Orange G. Obj. 8, 
oc. 6, tube length 153. 
Fic. 32. 32-cell stage. c.d., central blastomeres. __ Erlich’s haematoxylin. 
Obj. 4, oc. 6. 
Fic. 33. Part of egg after holoblastic cleavage has ceased. 4/., blastomeres 
from which nuclei surrounded by protoplasm are migrating. Borax carmine. 
Obj. 4, oc. 6. 
Fic. 34. Early blastoderm. ec., ectoderm ; #e., mesoderm ; y.m., yolk masses 
showing earlier position of blastomeres ; o.a., oblique division of ectoderm cells. 
Erlich’s haematoxylin. Obj. 6, oc. 6. : 
Fic. 35. Blastoderm formation completed. c.0., beginning of the precepha- 
lic organ; e#., entoderm cells; y.c., yolk cells; the rest as in Fig. 34. Borax 
carmine. Obj. 8, oc. 6. 
Fic. 36. Later stage of blastoderm. Letters as in Fig. 35. Borax carmine. 
Obj. 8, oc. 6. 
Fic. 37. Still later stage. Letters as in Fig. 35. Borax carmine. Obj. 4, 
Ocean. 
Fic. 38. Precephalic organ at its period of greatest development, blastoderm 
crenated. ¢;., first crenated membrane; remaining letters as before. Borax car- 
mine. Obj. 4, oc. I. 
Fic. 39. Precephalic organ elongated. cz., second crenated membrane; 4., 
knob where elongation is attached to crenated membrane number 2; remaining 
letters as above. Borax carmine. Obj. 4, oc. I. 
Fic. 40. Enlarged view of section of membranes and ectoderm of ovum. #., 
preparatory membrane; other letters as before. Borax carmine. Obj. 7g, oc. 6. 
Fic. 41. Entoderm cells showing vesicular protoplasm. Borax carmine. 
Obj. 2s, Oc. 4. 
