TABLE OF CONTENTS. 



PAGB 



physiology of the tissue-systems and of reproduction. The question 

 of old age. A comparison of the fern with the earthworm, and of 

 plants in general with animals in general. The physiological im- 

 portance of the chlorophylless plants 144 



CHAPTER XI. 



THE UNICELLULAR ORGANISMS. 



The multicellular body. Its origin in continued, but incomplete, cell- 

 division. The unicellular body. Its origin traced to complete cell- 

 division. The multicellular body and the unicellular body as 

 individuals. Unicellular forms physiologically " organisms." Special 

 importance of their structural simplicity. "Organisms reduced to 

 their lowest terms. " 156 



CHAPTER XII. 



UNICELLULAR ANIMALS. 

 A. Amceba. 



General Account. Habitat. Form. The " Proteus animalcule.'* Ap- 

 pearance. Pseudopodia. Locomotion. Foods. The encysted state. 

 Structure of the unicellular body. Cytoplasm. Nucleus. Vacuoles. 

 Reproduction by fission. Physiology. The fundamental physiological 

 properties of protoplasm as displayed in Aynoeba. The (question of 

 ■old age. Related forms. The Rhizopoda or pseudopodial Protozoa. 

 Arcella. Difflugia. The "sun-animalcule." The Foramenifera. 

 The Radiolaria , 158 



CHAPTER XIII. 



UNICELLULAR ANIMALS {Continued). 



B. Infusoria. 



General account. Habitat. The "slipper-animalcule." The "bell- 

 animalcule." Paramcecium. Its form, structure, and habits. Cyto- 

 plasm; trichocysts; vacuoles; nuclei; mouth; oesophagus; anal spot. 

 The encysted state. Reproduction by agamogenesis; by conjugation; 

 amphimixis. Voriicella. Its form, structure, etc. Its reproduction 

 by fission, endogenous division, and conjugation. Microgamete and 

 macrogamete. Related forms= Euglena; Zoothamnion; CarcJiesium; 

 Epistylis; etc. Physiology of the Infusoria. Herbivorous, carniv- 

 orous, and omnivorous infusoria. Analogy with higher forms. The 

 problem of chlorophyll in animals. S3^mbiosis. Vegetating animals. 

 The claim of unicellular animals to be regarded as unicellular "or- 

 ganisms"; organs in the cell; etc o 168 



