28 MICHIGAN ACADEMY OF SCIENCE. 



A^eloping animals to the influence of various factors of the environ- 

 ment in order to determine their effect. Developing e<2;gfi may be sub- 

 jected to different temperatures, or to chemical solutions of different 

 sorts and strengths or to the influence of electricity. In this way we 

 may find what influence each of these factors has on development. 

 Adult animals may be subject to similar changes of environment. The 

 results of such researches are usually expressible by mathematical 

 symbols, such as geometric curves or algebraic equations. 



i^uch work is only in the beginning but it may ultimately lead to 

 such an analysis of the environment as to enable us to assign to each of 

 its factors its proper value as an element in organic development. 



Experimental work is also being directed toward a determination 

 of the internal factors of development, those which are resident in the 

 animal itself and are not impressed upon it by the environment. The 

 effect of the removal of portions of the developing egg, enables us to 

 determine the part taken by those portions in the normal development 

 of the whole egg. Others of the internal factors of develojunent may 

 be studied by direct observation (without experiment) and by com- 

 parison. 



4. Toward a study of the activities of animals. Animals exhibit many 

 sorts of activities that may be classified. Those connected with the 

 taking of food, with reproduction, with the rearing of young, with con- 

 struction of dwellings, with community life and so on. We are begin- 

 ning to suspect that many of these activities have features that are 

 common to large numbers of animals and that their origin and de- 

 velopment may be traced with as much certainty as the origin and 

 development of the organs of the animals. Many of the activities of 

 man himself may doubtless be traced to an origin in the lower animals 

 and much light thereby thrown on what we are ])leased to call human 

 nature. 



Monographic work* in its descriptive branches, the study of varia- 

 tion experimental work, and the study and comparison of the activities 

 of animals seem then to be the directions in which zoological research 

 is now turning. 



The phylogenetic jihase has passed the height of its development for 

 the present and must await the accumulation of new data before it 

 can again become dominant. But since the study of phylogeny does 

 not really solve any philosophical (piestion (but only gives form to a 

 question already assumed to be solved) it is likely that it will never 

 again become ascendant. Time .will bring the solution of many of its 

 problems, but such solutions are likely in the future to possess only 

 secondary interest. 



On the other hand the new lines of work look toward the solution 

 of the most imi)ortant (juestions concerning the method of origin of 

 organic forms. 



Coincident with the gradual acceptance of the evolution idea, and 

 coincident with the great development of mori)hological and ]>hylo- 

 genetic ideas in our universities, there seems to have been a decline 

 in poi)ular activity in natural history. This did not become manifest 

 immediately after iSoO. but began. i»erha])s. ten or fifteen years after 

 that date and has been in pi-ogress since then, up very nearly to the 

 present time. 



