458 WILSON. 
EXPLANATION OF PLATE XX. 
Lumbricus communis. 
Fics. 66, 67, 68. Three cross-sections from the same series with Nos. 53 and 54 
(Pl. XVIII.). Fig. 66 is next to No. 54, and passes through the outer nephroblast on 
the left side. Fig. 67 is two sections anterior to No. 53, and passes through the right 
neuroblast and lateral teloblast (one of the nephroblasts of this side is shown in Fig. 
53, and the other appears in an adjoining section). Fig. 68 is several sections further 
forward. X 300. 
Fic. 69. Cross-sections through a slightly later stage (cf Fig. 94, Pl. XXII.), show- 
ing the cleavage of the mesoblast. X 300. 
Fic. 70. Adjoining section from the same series in the region of a dissepi- 
ment. X 300. 
Fic. 71. Cross-section of germ-bands, a little later than the last. The neural rows 
are entirely covered by the ectoblast. The nephric rows still lie at the surface. The 
lateral rows cannot clearly be distinguished. X 400. 
Fic. 72. Cross-section through the posterior part of an embryo at about the stage 
of Fig. 51, to show the dorsal extension of the germ-bands by migration, the middle 
stratum, the longitudinal muscle-bands, and the longitudinal vascular trunks. X 225. 
Fics. 73 To 78. Tangential longitudinal sections (somewhat oblique) from a series 
which shows the entire course of the mesoblastic and neural rows, with the correspond- 
ing teloblasts, the origin of the cephalic ganglia, head-mesoblast and Schluckzellen 
(see p. 415). The right primary mesoblast and the right neuroblast appear in No. 73; 
the left mesoblast in No. 75, the hinder part of the left mesoblastic band and the 
anterior part of the right in No. 77; the left mesoblast in Fig. 78, which passes 
through the middle line in front. X 300; No. 76, X 400. 
(All the figures with the camera.) 
