( 367 ) 

 TABLE XXXIX. 



Syptomntic Survey of the Sequence, according to Age, of the Tin-man 



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 EVOLUTION OF ORGANS. 



I. Skin and Intestinal Systems. 

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



l A I. Simple exoderm Gostra-ud* 



I. A. Skin-system l A 2. Outer skin (Skin-sensory layers and ) ,.. 



(OftUm* de> male) \ leather skin (Skin-fii runs l.t'yei ) f n l 



\ A 3. Outer skin, with hairs, glands, eic. Mammals 



B 1. Simple entoderm Gusliaiud* 



I. B. Intestinal syste 



B2. Intestinal epithelium (Intestinal-glan- ) 



dular layer) and inles inal muscular [ Worms 

 skin (Intestinal-fibrous layer) ) 



S3. Gill-intestine and stomach-intestine Chorda-.uiinials 



2. SECOND STAGE IN THE EVOLUTION OF ORGAN& 



II. Nerve and Muscle Systems. 

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



, T _ tCl. Upper throat ganglia Primitive Worn s 



II. C. Nerve-system c 2 ^^ medullary tube Chord*-anim.,ls 



(Systen eum) | c 3. Brain and spinal marrow Monorhina 



IT n MHS.-IP svstpm (/)l. Skin-muscle pouch Primitive Wo. ms 



^ 



8. THIRD STAGE IN THE EVOLUTION OF OKOAMS. 



III. Kidney and Vascular Systems. 



The two Systems first appear, one after the other, In the Soft-worm ancestors (.<*o?cuio). 



!E 1. Primitive kidney canala Scolecida 



A'2. Sopnental canals Acrania? 



E3. 1'iimitive kidneys Monorhina 



4. Permanent kidneys Protamnia 



f F 1. Simple ccelom Scolecida 



III. F. Vaocular system 1 /' 2. Dorsal and ventral vessels Worms 



(Systema vascalare) ~]F3. Heart (part of the ventral vessel) Chorda-an : mal.<< 



I f 4. Heart, with auricle and ventricle Monorhina 



4. FOURTH STAGE IN THE EVOLUTION OF ORGANS. 



IV. Skeleton and Sexual Systems. 



The two Sybtems first appear, one after the other, in the ChorJonia-ancestors. 



(Gl. Simple notochord Chorda-an'mals 



rV.(7. SkPloton-systera }G2. (.Cartilaginous (.rimitive skull Monorhina 



(Systeina slceUiare) ] G 3. Gill-arches, ribs, limbs Sebchii 



I. C 4. Limbs, with five digits Amphibia 



fHl. Simple hermaphrodite glands Chorda-animal* 



IV. //. Sexual system J H2. Distinct testes and ovaries Acrania 



(Systema sexuale) "j 7/3. Seed-duct and oviduct Selachil 



(lU. Phallus (penis, clitoru) Protamnia 



57 



