THE METAZOA DIVISION OF LABOR 211 



ADVANCED 



Hertwig, R., General Principles of Zoology. Henry Holt and Company. 



Miner, A Guide to the Sponge Alcove. Guide Leaflet, No. 23, American Museum 



of Natural History, New York. 



Parker, Elementary Biology. The Macmillan Company. 

 Parker and Haswell, Textbook of Zoology. The Macmillan Company. 

 Sedgwick and Wilson, General Biology. Henry Holt and Company. 

 Verworn, General Physiology. The Macmillan Company. 



