( 36; ) 



TABLE XXXIX. 



Systematic Survey of the Sequence, according to Age, of tho Ht 



Organ-systems. 

 (Phylogenetic Classification 01 Vertebrate Organs.) 



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

 organs probably first appeared.) 



1. FIBST STAGE IN THE EVOLUTION OP ORGANS. 



I. Skin and Intestinal Systems. 

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



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. 



IT r NPI-VP ivstPm ( c *' U PP er lhroat K in 8 lia Primitive Worms 



II. C. Nerve-system C 2. Simple medullary tube Chorda-animals 



(4MfcMa nerveuM) | Q 3 B| .. lin and spinal ' nlarrow Munorhina 



IT n MnoHo sir ( Z) 1. Skin-muscle pouch Primitive Worms 



II. D. Muscle system D sjde muscleg JJ tQ fc Acrania 



r 

 sem D sjde muscleg tQ 



mu SC aZar) ( /> 3 . Truilk ^ Umb musde8 



Fisue8 



8. THIRD STAGE IN THE EVOLUTION OP OKGAJIS. 



III. Kidney and Vascular Systems. 



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



!El. Primitive kidney canals Scolecida 



E2. Segmental canals Acrania? 



K3. Primitive kidneys Monorhina 



m. Permanent kidneys Protamnia 



i F I. Simple ccelora Rcolecida 



III. F. Vascular system ) F 2. Dorsal and ventral vessels Worms 



(Systetaa vascalare) "j F 3. Heart (part of the ventral vessel) Chorda-animals 



1^4. Heart, with auricle and ventricle Mouorhina 



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. 



(Gl. Simple notochord Chorda-snimals 



IV. O. Skeleton-system JG2. Cartilaginous primitive skull ftlonorhina 



(tiyttema skeletarc) ~) G 3. Gill-arches, ribs, limbs SeLichii 



l<?4. Limbs, with five digits Amphibia 



(HI. Simple hermaphrodite glands ("horda-animali 



IV. ff. Sexual system ) 111. Distinct testes and ovaries Acrania 



(Systema sexuale) ~\ 113. Serd-durt and oviduct Sc Lc-liii 



1^/4. Phallus (peuts, clitorU) Protamnia 



57 



