378 WHEELER. 
DESCRIPTION OF PLATE XVII. 
Blatta germanica, 
Fic. 39. Diagram of a median longitudinal section of an egg to show paths of 
nuclei, Explanation in the text. 
Fic. 40. Diagram of a transverse equatorial section of an egg to show paths of 
nuclei. Explanation.in the text. 
Fic. 41. Surface view of the ventral face of an egg 7} days old. cw, carina; fci, 
beginnings of procephalic lobes; 4/, depression (blastopore?) in the middle of the 
rounded area of proliferation. 
Fic. 42. Surface view of the ventral face of an egg 8 days old. a@s, amnion and 
serosa beginning; /c/, beginning of procephalic lobes. 
Fic. 43. Surface view of an embryo in “slipper” stage. @s, amnion and serosa. 
Fic. 44. Surface view of an embryo in the “ hammer” stage, 9} days old. 0, open- 
ing in amnion and serosa over the oral region; a, antennary lobe; /, beginning of 
the second thoracic appendage. 
Fic. 45. Embryo about 11 days old, isolated from the yolk. /, labrum; s¢, stomo- 
dum; cgi, brain; a¢, antennary lobe; md, mandible; mx}, mx, 1st and 2d maxille; 
p' to 7%, thoracic appendages; as, amnion and serosa; ¢f/, caudal plate. 
Fic. 46. Embryo just after rupture of amnion and serosa; about 14 days old. 4, 
cephalic end of yolk; oc, eye; ad, fat body, ast, anal stylets; f4, appendages of Ist 
abdominal segment; remaining references same as in Fig. 45. 
Fic. 47. Front view of same embryo. References the same as in Fig. 45. 
Fic. 48. Embryo almost ready to hatch. oc, eye; ¢g/, brain; g/*, infracesophageal 
ganglion; g/® to g/®, the three thoracic ganglia; g/1, last of the abdominal ganglia; 
oe, cesophagus; ¢, crop; gz, gizzard; Az, heart; s¢, stomach; vc¢, rectum; mpg, Mal- 
pighian vessels; as/, anal stylets; y, yolk; 2, labrum; zd, mandibles; mx! and 
mx, Ist and 2d maxille; /! to £3, thoracic appendages; a/, antenne. 
Fic. 49. Blatta germanica about a day after hatching. 
Fic. 50. Sagittal longitudinal section through the middle of the dorsal organ from 
an embryo 16 days old. a, anterior; 4, posterior end of dorsal organ; 0, depression; 
v, a yolk nucleus. 
Fic. 51. Frontal section through the anterior end of dorsal organ in an embryo 18 
days old. cc, heart; #7, nuclei of serosa cells; 0, cavity formed from the depression 
o, of Fig. 50; v, yolk nucleus. 
Fic. 52. Cross-section through the dorsum of an embryo to show formation of the 
heart. 4, cavity of heart; cé cb, cardioblasts; ecd, ectoderm; sm, somatic mesoderm; 
slm, splanchnic mesoderm; ex¢, entoderm; 4/, blood corpuscle becoming loosened 
from the wall of the heart; , yolk. 
Fic. 53. Cross-section through the thorax of an embryo 12 days old. #7, neural 
thickening; a, amnion; sv, serosa; v, yolk nucleus; sd, mesoderm; c/, coelomic 
cavity; #?, second pair of legs. 
Fic. 54. Cross-section through 2d maxillz of an embryo 16 days old. x?, second 
maxilla; g, duct of salivary gland; y, yolk; ev¢, entoderm; cé, cardioblast cells; 
remainder of references as in Fig. 53. 
Fic. 55. Cross-section through the basal abdominal somite of an embryo 26 days 
old. gi, ganglion; ad, corpus adiposum; 7, yolk nucleus; 7/7, tracheal opening; 4, 
yolk; cc, heart. 
