EXPLANATION OP PLATES I AND II, 



Figs. 30— 34.— Stage E. 



Fig. 30. Side view of straightened-out embryo. Antennae ringed. Buccal 

 fold (Z) extending round the jaw (j) on to the ventral surface. Sixteen 

 pairs of legs. Prasoral somite ventrally grooved. Apex of oral papilla 

 perforated. Length from front end of prasoral lobe to bend {d) 1'76 mm. 

 Eye still as an open pit (it is usually closed at this stage), d. Dorsal 

 ectodermal thickening, e. Eye. F. 1 .... ^c. Feet. _;'. Jaw. L. 

 Lip. or. p. Oral papilla, p. s. Praiioral somite. 

 Fig. 31. Embryo of same stage, in natural position in egg membrane. 

 Fig. 32. Hind end of embryo of same stage, ventral view. a. Anus. 



s. 20. 20th somite, s. 19 and 18. Legs of 19th and 18th somites. 

 Fig. 33. Ventral view of head and segments of jaws and oral papillae of 

 young embryo of same stage (E), Brain ungrooved. Ectoderm of 

 sides of mouth beginning to grow inwards («/.). Oral papillae perforated. 

 Opening of salivary glands (o. s.} at base of oral papillae. _;'. Jaw. 

 Z. Lips (buccal fold). M. Mouth, o. s. Opening of salivary gland. 

 p. s. praeoral somite, si. Ectodermal ingrowth at sides of posterior 

 part of mouth to form stomodaeum. 

 Fig. 34. Same view of slightly older embryo, with sides of mouth quite 

 infolded (sL) and a new posterior border to the mouth formed. Brain 

 still ungrooved. References as in Fig. 33. 

 Fig. 35. — Ventral view of head of embryo intermediate between Stages E 

 and P. Grooves in brain wide and shallow. The lips have grown considerably 

 and have extended behind the openings of the salivary glands, but have not 

 yet joined in the middle line. M. Antennae, c.ff. Groove in brain, j. Jaws. 

 i. s. Swelling at base of jaws. L. Lips. M. Mouth, or. p. Oral papillae 

 0. s. Opening of salivary glands. 



Fig. 36. — Stage P. Groove in brain almost closed ; the opening is slightly 

 wider anteriorly. Lips complete and folded, salivary opening quite covered by 

 them. Jaws completely enclosed. Swellings at base of jaws closely approxi- 

 mated so as to reduce the mouth opening to a narrow slit. The praeoral lobes 

 have completely united with one another (cf. Figs. 33 — 35). References as 

 in Fig. 35. 

 Figs. 37 and 38.— Stage G. 



Fig. 37. Side view of embryo of Stage G. Full number of legs and oral 

 papillae. Length 5 — 6 mm. An. p. Anal papillae. At. Antennae, 

 d. Dorsal ectodermal thickening. F. 1 — 17. The legs. me. Mesen- 

 teron. or. p. Oral papillae. R. Rectum, s. cf. Salivary glands, s. o. 

 i and 5. Segmental organs of 4th and 5th legs. si. g. Slime glands. 

 Fig. 38. Embryo of Stage G, curled up as in the uterus. 



