XIV CONTENTS. 



Page. 

 2. Nature of the Germs in the Viviparous Aphides and 



allied Insects, . . . . .191 



3. Nature of the Ephippial and Common Eggs in En- 



tomostraca and Rotifera, . . . 193 



4. Development of Unimpregnated Ova in certain In- 

 sects, ...... 196 



5. Occasional development of Unimpregnated Ovules 



in Plants, ..... 199 



G. Nature of the Viviparous Flowers of Plants, . 200 



7. Indications of a tendency to development in the 



Sexual Elements singly, . . . 202 



8. Essential community of nature between Ova and 



Gemmse, ...... 204 



9. Question of the necessary recurrence of Sexual 



Generation, ..... 206 



10. Bearing on the theory of Alternation of Generations, 208 



IX. SUMMARY OF CONCLUSIONS. 



1. Recapitulation of Results, - ... 212 



2. Formula of the Genetic Cycle, . . . 216 



3. Modification for the higher Animals, . . 216 



4. Extension for Pullulation, . . . 218 



5. Concluding Remarks, . . . 219 



X. CASES SIMULATING ALTERNATION OF GENERATIONS. 



1. Casual Alternation of Gemmation and Generation, 221 



2. Alternation of Diverse Gemmations, . 221 



3. Atavism, ..... 222 



4. Metamorphosis, ..... 223 



5. Spermatophores and Sporophores, . . . 225 



XI. HOMOLOGICAL RELATIONS OF THE STRUCTURES CONCERNED 



IN THE GENETIC CYCLE. 



1. Nature of the ultimate Sexual Elements, 229 



2. Homological Relations of the Germinal and Sper- 

 matic Elements, . 234 

 3. Links of the Genetic Cycle in the several Groups of 



Organized Beings, . . 237 



