Coe — A Century of Zoology in America. 387 



ress. Other taxononiic monographs published by this 

 museum include the various groups of animals from 

 many different parts of the world. 



A number of the larger State, municipal, and university 

 museums publish bulletins on special groups represented 

 in their collections as well as articles of general zoological 

 interest. 



Expeditions, subsidized by museum and private funds, 

 are from time to time sent to various parts of the world 

 and their results are often published in sumptuous 

 manner. 



The total number of living species of animals is 

 unknown, but considering that about a quarter of a mil- 

 lion new species have been described during the past 

 thirty years, it is probable that several million species are 

 in existence to-day. More than half a million have been 

 described. These are probably but a small fraction of 

 the number that have existed in past geological ages. 



Thus, in spite of all the work that has been done in sys- 

 tematic zoology and as the number of known species con- 

 tinues to increase, there still remain many groups of 

 animals, some of which are by no means rare or minute, 

 in which probably only a small proportion of the species 

 are as yet capable of identification. 



It is only since the publication of Ward and Whipple's 

 "Fresh-water Biology' ' within the past year that the 

 amateur zoologist could hope to find even the names of 

 all the organisms to be found in a single pool of water. 



During the past few years there has been a tendency on 

 the part of some of our biologists engaged in experimen- 

 tal work to disparage the studies of the systematists. It 

 must be granted, however, that both lines of work are 

 essential to the sound development of zoological science, 

 for experimental investigations in which the accurate 

 diagnosis of species is ignored always result in confusion. 



Ecology. — The marvelous modifications in structure 

 and instincts by which the various animals are adapted 

 to their surroundings now forms a special topic in biolog- 

 ical research and one of the most fascinating. The adap- 

 tations in habitat, time, behavior, appearance and even 

 in structure are found capable of a certain individual 

 modification when studied experimentally. 



Zoogeography. — Closely associated with systematic 

 zoology, and indeed a part of the subject in its broader 



