JOURNA.L OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE VII, 



Illustrating Enist Haeckel's memoir on the Gastraea-Theory, 

 the Phylogenetic Classification of the Animal Kingdom, 

 and the Homology of Germ-Lamellae. Translated by 

 E. Perceval Wright. 



Plate VII contains a schematic section througli the young stages of re- 

 presentatives of all the differeut phyla of Metazoa, and will give a clear idea, 

 not only of the homology of both primary germ-lamellse, but also of the origin 

 of the four secondary germ-lamellse. Figs. 1 — 8 are schematic longitudinal 

 sections ; figs. 9 — 16, schematic cross sections. In all the figures the 

 primary inner germ-lamella (ventral lamella, entoderm, vegetative germ- 

 lamella), including the parts derived therefrom, is indicated by the red colour ; 

 ■while, on the other hand, the primary outer germ-lamella (dermal lamella, 

 exoderm, animal germ -layer) is indicated by blue. The letters are through- 

 out the same. 



a. Primitive intestine (progaster) ; primitive intestinal tube. 



b. Ventral lateral hollow muscles. 



c. Ccelom (body-cavity or pleuro-peritoneal cavity). 



d. Intestinal glandular layer (mykogastral layer). 



e. Dermal layer (exoderm) ; outer primary germ-lamella ; intestinal 



layer. 



f. Fibro-intestinal layer (inogastral layer).' 

 h. Neuro-dermal layer. 



i. Gastral layer (entoderma) ; inner primary germ-lamella, dermal 



layer. 

 k. Germinal glands (appendages to the sexual glands). 

 I. Skin (coriuui). 



m. Fibro-dermal layer (inodermal layer). 

 n. Primitive brain (medullary canal). 

 o. Primitive mouth (prostoma) ; primitive oral opening. 

 r. Dorsal lateral hollow muscles. 

 t. Dorsal intestinal vessels (aorta). 

 tt. Primitive kidneys (excretions-canal). 

 X. Chorda dorsalis or vertebral column. 

 z. Ventral intestinal vessel (heart). 

 Pigs. I — 8 represent schematic longitudinal sections of gastrula from 

 eight diverse animal forms, i. e. — 



Fig. 1. — Gastrula of Sponges [Olynthis). 

 Fig. 2. „ „ Corals {Actinia). 



Fig. 3. „ „ Accelomi {Turbelland). 



Fig. 4. „ „ lunicata {Ascidia). 



Fig. 5. „ „ Mollusca(Z»««<eM«). 



Fig. 6. „ „ Asterida ( f//w/er). 



Fig. 7. „ „ Crustacea {Nauplius). 



Fig. 8. „ „ Vertebrata (AmpAioxus). 



Figs. 9 — 16 represent schematic cross-sections through representatives of 

 eight different, types, i. e. — 



Fig. 9. — Through a simple Sponge {Olynthus) or a simple Hydro- 

 medusa {Hydra). The wall of the primitive intestine re- 

 mains (as in Gastrula) for life only by the two primary gerui- 

 lameilse. 



