THIS BOOK IS DEDICATED TO 



all those xvJw have helped fo fmntd. to niahdam, 

 to direef. and to carry on the work oj the field 

 laboratories oj the world. To their efforts we owe 

 tunch of 07rr hioxvledge of the iiivertehrates. 



A few of the larger marine laboratories have become veritable 

 universities by the seashore, with summer classes, good research 

 facilities, and fine libraries. They maintain displays of living 

 animals that are of interest to any serious amateur naturalist 

 who may stop to visit. The smaller marine laboratories, as well 

 as those beside fresh waters or located in many terrestrial habi- 

 tats from the tundra to the tropical forest or desert, have more 

 modest facilities but are equally hospitable. Large or small, 

 these field laboratories, or biological stations, make their greatest 

 contribution by enabling scientists to live and work in places 

 where animals can be studied in their natural surroundings. 



