477 
off from the primitive vesicle at the same time with the lateral sacs, 
and connects the latter dorsally. 
The deepening and coming together of the peribranchial folds 
Fig. L Fig. 3. 
Fig. 1. Portion of inner vesicle on right side in posterior region, cut transversely, 
showing rudiment of pericardium, pe. r.; a and 5 nuclei passing into latter; mm. v. 
inner vesicle. (500 Diam.) 
Fig. 2. Frontal section of anterior end of inner vesicle, showing very young 
rudiment of dorsal tube, d. t. r,, cut transversely; ec ectoderm is also figured; im, v. 
inner vesicle. (500 Diam.) 
Fig. 3. Transverse section from anterior end of older bud; gl. r., rudiment of 
ganglion; d. t. dorsal tube; ec ectoderm; in. v. inner vesicle. (500 Diam.) 
Fig. 4. Transverse section from still older bud, showing origin of subneura] gland, 
8, mn. g., from ventral wall of dorsal tube, d, t. g.; gl ganglion. (500 Diam.) 
