462 WILSON. 
EXPLANATION OF PLATE XXII. 
Fig. 89 from rea fetidus ; the others from Z. communis. 
Fic. 89. Surface view of part of the dorsal wall of an embryo in the stage of Fig. 
50, showing a few of the large ectoblast cells (or their nuclei), the branching muscle- 
cells and the amceboid cells (1) of the migratory mesoblast. ’ X 400. 
Fic. 90. Part of cross-section through posterior part of an embryo of about the 
same age as Fig. 51, in the region where concrescence of the neural cords is in prog- 
ress; the section passes through the commissures, and the neural rows are com- 
pletely separated from one another. X 400. 
Fic. 91. Section from the same series two sections behind the last, in the re- 
gion of a pair of ganglia; the neural rows are connected above by a bridge of neural 
tissue. X 400. 
Fic. 92. Longitudinal section (drawn by combining sketches of two adjoining sec- 
tions) a little to the side of the one shown in Fig. 80, showing the ciliated canal of 
the head-kidney embedded in the dorsal wall of the archenteron. X 400. 
Fic. 93. Longitudinal section showing the setigerous glands, dissepiments, ventro- 
lateral blood-vessels and portions of the nephridia in a stage about like that shown in 
Fig. 51. X 300. 
Fic. 94. Sagittal section through the posterior part of an embryo (like Fig. 51) 
shortly before the formation of the proctodeeum, The neural rows end abruptly be- 
hind, and the primary mesoblasts are the only teloblasts remaining. X 300. 
Fic. 95. Section from posterior part of a transverse series of an embryo just before 
hatching. Owing to the upward curvature of the hinder part of the body, the sec- 
tion passes nearly horizontally through the germ-bands. The mesoblastic bands are 
in contact at their hinder ends; the lateral cell-rows end abruptly behind. X 225. 
Fic. 96. Section from the same series, five sections further forward, cutting the 
hinder part of the germ-bands transversely and the proctodzal invagination vertically. 
The primary mesoblasts have disappeared; the mesoblastic bands can be traced 
around the proctodeum and meet on the dorsal side. Sar225- 
Fic. 97. Sagittal section (corresponding precisely to No. 94, but a little further 
toward the side) passing through one of the mesoblastic bands and through the broad 
proctodzeal invagination. The latter is deepest ventrally and fades away towards its 
anterior lip. The tip of the mesoblastic band represents the former position of the 
primary mesoblast. ‘i X 350. 
(All of the figures drawn with the camera.) 
