Xll 



co:ntents. 



III. — Survey of the Reproductive Process in the 



Animal Kingdom. 



Page. 



1. — General Character of the Process, . . 68 



2. — Reproduction in the Protozoa, ... 74 



3. — In the Coeleuterata, .... 81 



4. — In the Echinodermata, .... 84 



5. — In the Polyzoa, ..... 87 



6. — In the Tiinicata, ..... 89 



7. — In the higher MoUusca, .... 91 



8. — In the Hehnintha, .... 94 



9. — In the AnneHda, .... 99 



10. — In the higher Articnlata, . . . 102 



11. — In the Vertebrata, .... 106 



12. — Concluding Remarks, .... 107 



IV. — Nature and Varieties of Alternation of Gene- 

 rations. 



1. — Points of Agreement and Diversity in cases of Al- 

 ternation, ..... 109 



2. — Protomorphic Alternation, as in the Trematoda, 

 from Gemmation in the Early Stage of Develop- 

 ment, ...... 112 



3. — Gamomorphic Alternation, as in the Poly^Difera, 



from a later Gemmation, in the evolution of Sex, 117 



4. — Relations of these two forms of Alternation, . 128 



5. — Their Co-existence in the case of the Cestoid Worms, 131 



6. — Ortlwmorphic Alternation, as in the Aphides, from 

 Gemmation in the evolution of the Typical Or- 

 ganization, ..... 133 



7. — Reference of the best known cases of Alternation, 



to one or other of the foregoing heads, . 136 



8. — Co-existence of all the three forms in the case of 



some Annelida, ..... 137 



9. — Alternation in the Salpce, .... 140 



10. — Protomorphic and Gamomorpliic Alternation in 



Mosses and Ferns among Plants, . . 142 



V. — PULLULATION. 



1. — Notice of a Series of Successive Gemmations, inter- 

 polated at certain points. 



146 



