The Origin of Vertebrates

Theories of the origin of vertebrates--Importance of the central nervous system--Evolution of tissues--Evidence of Palæontology-- Reasons for choosing Ammocoetes rather than Amp...

Different kinds of eye--Simple and compound retinas--Upright and inverted retinas--Median eyes--Median or pineal eyes of Ammocoetes and their optic ganglia--Comparison with othe...

The bony and cartilaginous skeleton considered, not the notochord-- Nature of the earliest cartilaginous skeleton--The mesosomatic skeleton of Ammocoetes; its topographical arra...

Branchiæ considered as internal branchial appendages--Innervation of branchial segments--Cranial region older than spinal--Three-root system of cranial nerves: dorsal, lateral,...

The value of the appendage-unit in non-branchial segments--The double nature of the hyoid segment--Its branchial part--Its thyroid part-- The double nature of the opercular appe...

Fishes divided into Amphirhinæ and Monorhinæ--Nasal tube of the lamprey--Its termination at the infundibulum--The olfactory organs of the scorpion group--The camerostome--Its fo...

Comparison of the trigeminal with the prosomatic region--The prosomatic appendages of the Gigantostraca--Their number and nature--Endognaths and ectognath--The metastoma--The co...

The prosomatic segments of the vertebrate--Number of segments belonging to the trigeminal nerve-group--History of cranial segments--Eye-muscles and their nerves--Comparison with...

The prosomatic region in Ammocoetes--The suctorial apparatus of the adult Petromyzon--Its origin in Ammocoetes--Its derivation from appendages--The segment of the lower lip or t...

The nose of the Osteostraci--Comparison of head-shield of Ammocoetes and of Cephalaspis--Ammocoetes only living representative of these ancient fishes--Formation of cranium--Clo...

Lateral line organs--Function of this group of organs--Poriferous sense-organs on the appendages in Limulus--Branchial sense-organs-- Prosomatic sense-organs--Flabellum--Its str...

Difference between cranial and spinal regions--Absence of lateral root--Meristic variation--Segmentation of coelom--Segmental excretory organs--Development of nephric organs; pr...

Relationship between notochord and gut--Position of unsegmented tube of notochord--Origin of notochord from a median groove--Its function as an accessory digestive tube--Formati...

The law of recapitulation--Vindication of this law by the theory advanced in this book--The germ-layer theory--Its present position-- A physiological not a morphological concept...

Giant nerve-cells and giant nerve-fibres; their comparison in fishes and arthropods; blood- and lymph-corpuscles; nature of the skin; origin of system of unstriped muscles; orig...

occurring between A and B will throw the retinal sense-cells with the optic nerve further from the surface, and the layers B and A between the retina and the source of light wil...

of the mesosomatic appendages. This is, of course, exactly what is found for the muscles which move the lateral eyes of the vertebrate; these muscles, innervated by the IIIrd, I...

nerves of the vertebrate have been derived from the prosomatic group of nerves of the invertebrate can be put to the test by the answers to the following morphological and anato...

We see, then, that the conception of a syncytial neuro-epithelial host holding in its meshes a number of free cells leads directly to the questions: What is the coelom? To which...