xn CONTENTS. 



pxav 



tion of the Skull from the Head-plates. — Gill-openings and Gill- 



arohes. — Sense-organs. — Limbs. — The Two Front Limbs and the 

 Two Hind Limbs 328 



CHAPTER XII. 



THE GEKM-MEMBRANES AND THE FIRST CmCULATION OP 



THE BLOOD. 



The Mammalian Organization of IMan. — Man has the same Bodily i 



Structure as all other Mammals, and his Embryo develops in » 

 exactly the same way. — In its Later Stages the Human Embryo is 



not essentially different from those of the Higher Mammals, and in  



its Earlier Stages not even from those of all Higher Vertebrates. — J 

 The Law of the Ontogenetic Connection of Systematically Belated 



Forms. — Application of this Law to Man. — Form and Size of the : 



Human Embryo in the First Four Weeks. — The Human Embryo iu i 



the First Month of its Development is formed exactly like that of ! 



any other Mammal. — In the Second Month the First Noticeable ; 



Differences appear. — At first, the Human Embryo resembles those ; 



of all other Mammals ; later, it resembles only those of the Higher ' 



Mammals. — The Appendages and Membranes of the Human • 



Embryo. — The Yelk-sac. — The Allantois and the Placenta. — The j 

 Amnion. — The Heart, the First Blood-vessels, and the First Blood, 

 arise from the Intestinal-fibrous Layer. — The Heart separates 



itself from the Wall of the Anterior Intestine. — The First ' 



Circulation of the Blood in the Germ-area (a. germinafiva) : Yelk- ' 



arteries and Yelk-veins. — Second Embryonic Circulation of the 1 



Blood, in the Allantois : Navel-arteries and Navel-veins. — Divisions ] 



of Human Germ-history r'>G3 i 



CHAPTEH XIIL ' 



THE STRUCTURE OF THE BODY OF THE AMPHIOXUS AND 



OF THE ASCIDIAN. ! 



i 



Causal Significance of the Fundamental Law of Biogeny. — Influence I 



of Shortened and Vitiated Heredity. — Kenogenetic Modification of ' 



Palingenesis. — The Method of Phylogeny based on the Method of ' 



Geology. — Hypothetic Completion of the Connected Evolutionary 3 



Series by Apposition of the Actual Fragments. — Phylogenetio ! 



Hypotheses are Reliable and Justified. — Importance of the Amphi- I 



1 



1 

 I 



