PREFATORY NOTE. 



When the first volume of these lectures was offered in 1890, 

 their continuance as an annual publication was thought of only 

 as a possibility ; it was not promised, nor, indeed, suggested. 

 The usefulness of such lectures had only been tested by a 

 single summer's experience; and, although it was certain that 

 they served a good purpose in the work of the Laboratory, the 

 advisability of publishing them was doubtful. While the recep- 

 tion accorded to the two volumes already issued indicates that 

 it would not now be presumptuous to announce the hope of 

 continuing them, it would be rash to promise this in the 

 present state of uncertainty regarding the future of the Labor- 

 atory. The Laboratory is an experiment to test the extent of 

 our need, and the possibility of securing general co-operation. 

 It has furnished a demonstration in both these respects ; but 

 it remains to be seen whether this will suffice to bring to it the 

 necessary foundation of a large endowment. Special thanks 

 are due to those who, in reviewing the " Biological Lectures," 

 have called attention to the nature and purpose of this experi- 

 ment, and to the high importance of the end proposed. The 

 project appeals, not for government support, but to private 

 munificence, and every authoritative confirmation of its merits 

 adds strength to our effort. 



The general aim and purpose of these lectures and the place 

 they take in our work have been already defined. ^ Nearly 

 every lecture of the present volume deals with one or other 

 side of the problem of organic development — that problem 

 which has led, and which will most likely ever continue to lead, 

 the biological sciences. The sister sciences dealing with the 

 evolution of the inorganic world are our natural allies and co- 

 adjutors, laboring to the same end though in different fields. 



^ Preface to volume II, 



