TABLE OF CONTENT-. 5 



Page 

 Organs of circulation 51 



Heart i;i 



.Arteries and veins .......... 62 



Eeart and vessels of vertebrates . . .... 64 



Ori/unx nj- rcxjii riitinii ........... 67 



Branchiae 69 



Lungs, trachea? 69 



Trachea! gills 71 



Renewal of external medium 72 



Venous and arterial blood . . ... ... . .73 



Animal lu-at. 73 



' Organs of secretion .......... 74 



Kidneys 75 



Water-vascular vessels and segmental organs 75 



Vertebrate kidneys 76 



Cutaneous glands 77 



ORGANS OF ANIMAL LIFE 78 



ShrlrtaJ structure.-* .......... 79 



Xi'rroiix xijxti-m 79 



Si-tisc organ* S3 



Tactile organs 84 



Auditory organs 85 



Visual organs 85 



Facetted eye 88 



Simple eye .89 



Olfactory organs 91 



INTELLIGENCE AND INSTINCT 93 



REPRODUCTIVE ORGANS 95 



Biogenesis 96 



Asexual reproduction 96 



Sexual reproduction 97 



Hermaphroditism 99 



Separation of the sexes 100 



Sexual differences 101 



Sexual dimorphism 104 



Parthenogenesis 105 



DEVELOPMENT .... .107 



Fertilisation of the ovum 108 



Segmentation of the ovum 110 



Food-yolk Ill 



Blastosphere 113 



Formation of gastmLa 114 



Primitive streak 115 



Germinal layers .116 



Theory of Gastrrea 117 



DIRECT DEVELOPMENT AND METAMORPHOSIS ]19 



Effect of food-yolk on development 120 



Explanation of Metamorphosis 121 



ALTERNATION OF GENERATIONS. POLYMORPHISM AND HETEROGAMY 123 



Metagenesis 123 



Explanation of Metagenesis 124 



Polymorphism 126 



Heterogamy 127 



Predogenesis 128 



Hetcrogamv of Trematoda . 129 



