240 F. G. HEATHCOTE. 



Fig. 28. — Longitudinal vertical section through first post-cephalic segment 

 of a slightly later embryo than Fig. 27. som. m. Somatic mesoderm. 

 ec. Ectoderm. mem. ex. Membranous envelope. sp. m. Splanchnic meso- 

 derm, cav. in mes. Cavity in mesoderm. (Zeiss, D.) 



Fig. 29. — Longitudinal vertical section through part of a tenth day embryo, 

 to show ventral flexure. sp. m. Splanchnic mesoderm, som. m. Somatic 

 mesoderm, v.f. Ventral flexure. (Zeiss, r.) 



Fig. 30. — Longitudinal vertical section through embryo rather later than 

 Fig. 29, to show ventral flexure, ec. Ectoderm, mes. Mesoderm, v.f. Ven- 

 tral flexure. 



Fig. 31.— Transverse section through late tenth day embryo, to show ner- 

 vous system, sp. m. Splanchnic mesoderm, som. m. Somatic mesoderm, ec. 

 Ectoderm. ec. th. Ectodermal thickening. Ion. fur. Longitudinal furrow 

 between nerve-cords, en. Endoderm forming gut. (Zeiss, d.) 



Fig. 32. — Ventral part of a transverse section through an embryo of the 

 eleventh day, to show the nerve-cord and the Malpighian tubes. This section 

 is taken in the posterior region, about the sixth segment, som. m£s. Somatic 

 mesoderm. gl. Ganglia. Malp. t. Malpighian tubes, pr. Proctodseum- 

 sp. mes. Splanchnic mesoderm, y. s. Yolk-spherules, v. ec. Ventral ectoderm. 

 b. c. Part of body cavity between the nerve-cord and ventral ectoderm. 

 (Zeiss, u.) 



Fig. 33. — Vertical longitudinal section through part of a twelfth day 

 embryo, to show the stomodseum. sub. gl. Suboesophageal ganglion, supraoe, 

 Supraoesophageal ganglion, st. Stomodaeum. In this section the supra- and 

 sub-oesophageal ganglia are not cut exactly in the middle line, and so appear 

 smaller than they really are. (Zeiss, d.) 



Fig. 34. — Transverse section through a twelfth day embryo in posterior 

 region of body. gl. Ganglia of nerve-cord. r. app. Rudiment of appendage, 

 wws. Mesoderm forming a partition to the body cavity, pr. Proctodaeum. 

 Malp. t. Malpighian tubes, m. en. Mesoderm cells in the body cavity derived 

 directly from the endoderm. 



All the figures were drawn by myself under a Zeiss's camera lucida. 



