viii GENERAL BIOLOGY 



have the further aid of generous colleagues toward their 

 early elimination. • 



Many of my colleagues and former pupils have helped me 

 with valuable suggestions and I would be glad if there were 

 space to thank them all; and I cannot refrain from making 

 mention of the special help that has been given me by Pro- 

 fessors J. H. Comstock, W. A. Riley, G. F. Atkinson, B. M. 

 Duggar, B. F. Kingsbury, I. M. Bentley, A. Hunter, R. H. 

 McKee and Drs. A. H. Wright and W. A. Hilton on the 

 part of the proofs that they have seen. Others of my 

 colleagues have generously loaned me valuable portraits, 

 concurring in my belief, that it would be worth while to 

 introduce the faces of at least a few of the great pioneers 

 of biology unobtrusively into the students' intellectual 

 environment. 



This book exists for the sake of the practical studies con- 

 tained in it. Mere attendance on a lecture course does not 

 amount to much; for in biology, as in other subjects, it is 

 only those who handle the raw materials and build up with 

 them, who can ever really comprehend the superstructure. 



James G. Needham. 



