THE GASTRAEA-THEORY, ETC. 



245 



II. — Synoptical Table of those Primitive Organs loliich, ivith 

 probability, are considered as homologous in the Vermes, 

 Articulata, Molluscous and Vertebrated Animals. 



Vermes. 



Aethbopoda. 



MOLLUSCA. 



Veetebeata. 



I. — Products differentiated from the Neuro-dermal Layer. 



Epidermis. 



Primitive brain 



(upper oesophageal 



ganglia). 



Organs of excre- 

 tion 

 (" water vascular, 

 segmental or- 

 gans"). 



Hypodermis 

 (chitine mem- 

 brane). 



Brain 



(upper oesophageal 



of 



Shell-glands 

 Crustacea. 



Epidermis. 



Brain 



(upper oesophageal 

 ganglia). 



Kidneys. 



Epidermis. 



Marrow-bone or 



medullary tube 



(foremost part). 



Primitive kidney 

 processes. 



II. — Products differentiated from the Fiiro-dermal Layer. 



Corium 

 (and annular mus- 

 cular sheath). 



Straight muscular 

 sheath. 



Corium (rudi- 

 ment). 



Hollow muscles 

 (longitudinal). 



Corium and Corium and dermal 

 dermal muscles i muscles 



(First appearance!) (First appearance!) 



Inner hollow mus- 

 cles. 



Lateral hollow 

 muscles. 



III. — Products differentiated from the Fibro-intestinal Layer. 



Coelom, 



Principal dorsal 

 vessels. 



Principal ventral 



vessels. 



Intestinal wall 

 (exclusive of epi- 

 thelium). 



Body cavity. 



Heart. 



Intestinal wall 

 (exclusive of epi- 

 thelium). 



Body cavity. 



Ventricles. 



Intestinal wall 

 (exclusive of epi- 

 thelium). 



Pleui'o-peritoneal 

 cavity. 



Aorta (primordi- 

 alis). 



Heart (together 

 with bulbus arte- 

 riosus). 



Fibro-intestinal 

 layer and mesen- 

 tery. 



IV. — Products differentiated from the Intestinal Glandular Layer. 



Intestinal epithe- 

 lium. 



Intestinal hypo- 

 dermis (for the 

 most part). 



Intestinal epithe- 

 lium (for the most 

 part). 



Intestinal epithe- 

 lium (excepting 

 mouth and anus). 



