( 3<57 ) 

 TABLE XXXIX. 



Systematic Snrvey of the Sequence, according to Age, of the Human 

 Organ-systems. 

 (Phylogenetic Classification of Vertebrate Organs.) 

 (On the right are given the Ancestral Stages, in which the respective 

 organs probably first appeared. ) 



1. First Stage in the Evolbtiox op Okqaks. 



I. Skin and Intestinal Systems. 



The two Systems appear first, and simultaneously, in the Gastread ancestors. 



I. .4. Skin-system \ .4 2. Outer sliin (Skin-sensory Layerl ^°d ) ,y 



(^Systema dermale) \ leather sltin (Skin-fiurous layer) | 



1^3. Outer skin, with hairs, glands, eic. Mammals 



SB I. Simple entoderm Gastraads 



B 2. Intestinal epithelium (Intestinal-glan- \ 

 dular layer) and intesiinal muscular Worms 

 skin CIntestinal-flbrous layer) ) 



B 3. Gill-intestine and stomach-intestine Chorda-aTiimals 



2. Second Stage in the Evolution op Organs. 



II. Nerve and Muscle Systems. 



The two Systems appear first, and simultaneously, in the Primitive Worm ancestors. 



TT ^ -VT <■ /CI. Upper throat gringlia Primitive Worms 



11. C. JNerve-system ^2. Simple medullary tube Chorda-animals 



iSystenta nerveum) j ^ 3^ ^^^^^ ^„^j g^j^^j marrow Monorhii.a 



_. _ ,, , . /i> 1. Skin-muscle pouch Primitive Worms 



II. D. Muscle-system ^3. Side muscles of the trunk Acrania 



3. Third Stage in the Evolution of Organs. 



III. Kidney and Vascular Systems. 



The two Systems first appear, one after the other, in the Soft-worm ancestors (^Scolecida'). 



SEl. Primitive kidney canals Scolecid^ 



JE2. Segmental canals Acrania? 



JB3. Primitive kidneys Monorhina 



U 4. Permanent kidneys Protamnia 



rFl. Simple coelom Scolecida 



III. J^. Vascular system ] F2. Dorsal and ventral vessels Worms 



(^Systema vasculare) "^ F3. Heart (part of the ventral vessel) Chorda-animals 



\F^. Heart, with auricle and ventricle Monorhina 



4. Fourth Stage in the Evolution op Organs, 



IV. Skeleton and Sexual Systems. 



The two Systems first appear, one after the other, in the Chordonia-ancestors- 



r (7 I. Simple notochord Chorda-animals 



IV. ff. Skeleton -system ) G2. Cartilaginous primitive skull Monorhina 



iSystema skeUtare) j <? 3. Gill-arches, ribs, limbs Selachii 



Lg4. Limbs, with five digits Amphibia 



/".ffl. Simple hermaphrodite glands Chorda-animals 



IV. S. Sexual system | H2. Distinct testes and ovaries Acrania 



iSysiema sexuaW) J ^3. Seed-duct and oviduct Selachii 



Vi^4. Phallus (penis, clitoris) Protamnia 



39 



