78 -A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



began to go beyond his immediate horizon. He became more and more restricted 

 to observation of what can be seen or inferred only from the complete organism, 

 without any regard to what goes on within it or to the way in which what s'oes 

 on within it conditions its activities. He himself began to build a fence around 

 his own thinking as it were and finally to lose all connection with the workers in 

 these special fields. 



Conversely, the knowledge of these special fields ultimately came in many 

 instances to be so detailed that it seemed almost beyond the range of any one 

 person to grasp more than one of them. Not only was natural history crowded 

 out but also the specialized fields began to elbow each other. Witness what hap- 

 pened to comparative anatomy, which is the term generally used if one is study- 

 ing the structure of vertebrates, and comparative morphology, a term that has 

 come to have the same meaning if one is studying certain invertebrates. The 

 great era of comparative anatomy began with Cuvier in the early years of the 

 nineteenth century and lasted to about 1900. During its early stages it could 

 very well be included under natural history, but it developed into a specialty by 

 itself and in turn came into competition with the rising studies of cytology and 

 histology and physiology, which last was more concerned with what goes on 

 within the tissues than in how they are put together. And at last, coincident 

 with the rise of genetics, comparative anatomy almost faded from the scene. 



During the rise of the various specialties in biology great masses of detailed 

 information have been accumulated, making it difficult for anyone not immedi- 

 ately concerned with these specialties to master their content. This has been 

 seemingly inevitable, for the first necessity in the development of any field is 

 merely to accumulate facts. Eventually, however, these facts lead to the devel- 

 opment of theories and principles and then to a degree of simplification. The 

 pertinent facts are sorted out, the principles are established, and in time a stage 

 is reached when it is no longer necessary to have all the details at one's fingertips 

 in order to appreciate the bearing of a particular discipline upon other disci- 

 plines. When that stage has been reached, the general student does not need to 

 know all the details that have been worked out about the physiology of the cell, 

 but he does need to know the principles involved. And we are coming to the 

 point where those principles are being formulated in such a way that it is possible 

 to grasp them and their implications for workers in other fields. In other words, 

 we are coming to the point where the general student can begin to get an under- 

 standing of the principles that are involved in many fields and which have a 

 bearing upon the special field in which he is engaged. 



Thus the principles of genetics have a very profound Ijearing upon the work 

 of the systematist especially as it concerns species. They even have a bearing 

 upon the work of the student of comparative morphology. Conversely, the work 

 of the systematist has a profound bearing upon the broader problems of genetics 

 and I feel sure that the comparative morphology of the arthropods, for example, 

 Avill, when well enough developed, have a profound bearing upon conclusions 

 derived from genetics. 



So we are coming once more to a situation in which the person of broad inter- 

 est need not necessarily have to be a master of all the details of all these spe- 

 cialties. He need concern himself only with the principles — with perhaps enough 

 knowledge of details to understand those principles. He is to a degree freed irom 



