( 367 ) 

 TABLE XXXIX. 



8y B tem atio Snrvey of the Sequence, according to Age, of the Hi 



Organ-systems. 



(Phylogenetic Classification of Vertebrate Organs.) 

 (On the right are given the Ancestral Stages, 'n which the respective 

 organs probably first appeared.) 



1. FiBST Stage in the ETOLrrroy of Ohgajti. 



I. Skin and Intestinal Systems. 



Tbe two Systems appear first, and simultaneously, in the Oaatread aaeetton. 



I A 1. Simple exoderm (Hstreafdi 



A 2. Outer skin (Skin-sensory layer) and ) Worms 

 leather skin (Skin-fibrous layer) j 

 A 3. Outer skin, with hairs, glands, etc. Mammals 



!£ 1. Simple entoderm Gastneads 



B 2. Intestinal epithelium (Intestlnal-glan- '\ 

 dular layer) and intestinal muscular \ WorBis 

 skin (Intestinal-fibrous layer) ) 



B 3. Gill-intestine and stomach -intestine Ghorda-anim*lB 



S. Second Stage is the Evolution op Obqamb. 

 II. Nerve and Muscle Systems. 

 Tke two Sjitems appear first, and simultaneously, in the PrimitiT* Warm aooestors. 



n r Nprve svstem I ^ ^- ^PP^"" ^^^^^^ S-nglia Primitive Worms 



11. U. jNerve-sysiem ^2. Simple medullary tube Chorda-animals 



iSystema nervtam) ( ^ 3 3,.^/^ ^^^ spinal marrow Monorhina 



TT n M«o,,i» Q,To*a»« lD\. Skin-muscle pouch Primitive Worms 



"^w™ SvJ«r-^ \ ^ 2- Side muscles of the trunk Acrania 



iSyitaaa mtocotore) | ^ 3 ^^^^j^ ^^ ^^^ muscles Fishes 



8. Third Stage in the Evolution of Oboajm^ 



III. Kidney and Vascular Systems. 



TW tw« Systems first appear, one after the other. In the Soft-wona ABoeskon (JSKUcida). 



1^1. Primitive kidney canAli Scolecida 



^2. Segmental canals Acrania? 



^3. Primitive kidneys Monorhina 



E4,. Permanent kidneys Ptotamnia 



ri^l. Simple coelom Scolecida 



OL F. Vascular system \ F2. Dorsal and ventral vessel* Worms 



{Syitema vatculare) j /«' 3. Heart (part of the ventral vewel) Chorda-animals 



I J? 4. Heart, with auricle and ventricle Monorhina 



4. FouBTH Stage in the Evolution of Osgani. 



rV. Skeleton and Sexual Systems. 



Tbe two Systems first appear, one after tbe other, in the Cliordonia-anceston. 



/-(? 1. Simple notochord Chorda-animals 



IV. O. ^eleton-system J G 2. Cartilaginous primitive ikoU Monorhina 



{SysteiMk $ktUtare) J (? 3. Gill-arches, ribs, limbs Selachii 



V. 6^ 4. Limbs, with five digits Amphibia 



{^1. Simple hermaphrodite glands Chorda-animala 



H2. Distinct testes and ovaries Acrania 



JI3. Seed-duct and oviduct Selachii 



^4. Phallus (penis, clitoris) Piotamnia 



57 



