CONTEXTS. xi 



X. 



FRESH-WATER POLYPES. 



Habit and form Naked-eye appearances Mode of feeding Mul- 

 tiplication Microscopic structure Relationships to simpler plants and 

 animals Laboratory work p. 98 106. 



XL 



THE FRESH-WATER MUSSEL. 



General structure Respiratory organs Alimentary organs Circu- 

 latory system Excretory organs Reproductive organs Development 

 Laboratory work. ....... p. 107 126. 



XII. 



THE FRESH-WATER CRAYFISH AND THE LOBSTER. 



Habitat General structure Appendages Segments Alimentary 

 canal Circulatory organs Respiratory organs The green glands 

 Nervous system Sense organs Reproductive organs Development 

 Laboratory work. ....... p. 127 158. 



XIII. 



THE FROG. 



General characters Development Specific characters of Rana tem- 

 poraria and R. esculenta The pleuroperitoneal cavity and the alimen- 

 tary canal The neural canal and the cerebro-spinal axis Objects seen 

 on transverse sections at various points Comparison with lobster The 

 skeleton The digestive system The blood and lymph vascular systems 

 The ductless glands The respiratory organs The urinary organs 

 The generative organs The nervous system The sense organs La- 

 boratory work. ........ p. 159 267. 



APPENDIX p. 268. 



