NOVEMBEB 25, 1904.] 



SCIENCE. 



703 



In still another way are the dynamical 

 and static characteristics bound together, 

 for every form or part has not merely a 

 form or function, but a development, and 

 development is a dynamical process. A 

 decade or two ago embryological develop- 

 ment was regarded as a purely morpholog- 

 ical subject, as a series of stages, and little 

 attention was paid to the causes that pro- 

 duce the stages and the succession of 

 organs. During the last decade, however, 

 partly under the stimulus of physiologists 

 who have entered the field of embryology, 

 its dynamical problems have been studied 

 also by morphologists. As a result of the 

 researches of Loeb, Driesch, Herbst, E. B. 

 Wilson, Morgan and many others we have 

 come to recognize that the egg is organized 

 — cytoplasm as well as nucleus— and that 

 it exhibits varying degrees of organization 

 in different cases. Sometimes it seems as 

 though every part of the egg was toti- 

 potent, as in the medusae; in other cases, 

 the different parts of the cytoplasm seem 

 told off to develop into particular and 

 definite organs, as in some molluscs. We 

 have learned, further, that at every stage 

 new organs are called forth and their de- 

 velopment directed by stimuli proceeding 

 from already existing organs. 



Moreover, it has been found that even 

 adult structures are dependent upon ex- 

 ternal conditions for their form. It ap- 

 pears that peculiar functioning may alter 

 the form of internal organs, as has been 

 demonstrated in the case of a ship's trim- 

 mer and of a cobbler by Lane, and as a vast 

 number of pathological cases testify, such 

 as the alteration of the arrangement of 

 plates in the spongy tissue in the head of 

 the femur, and the functional hypertrophy 

 of the other kidney after the loss of one. 

 Morphologists have been forced to realize 

 that form and structure can not be dealt 

 with aside from function and behavior. 

 Every part of the living body is a sensitive 



responding part whose sensitiveness de^ 

 termines structure. This is seen particu- 

 larly well when the body is mutilated or a 

 part removed; then begins the wonderful 

 process of regeneration or regulation by 

 which, under control (in the higher ani- 

 mals) of the nervous systeni, the lost parts 

 are in many cases restored. In truth, the 

 work of the morphologist has extended into 

 the realm of the form-developing and form- 

 maintaining factors and this is a physiolog- 

 ical realm. 



From these experiences I conclude that 

 the morphologist who studies form char- 

 acteristics only is too narrow. Character- 

 istics in their twofold aspect of form and 

 function should be the object of his in- 

 vestigations—their difference in allied spe- 

 cies, their integrity, their behavior in 

 breeding, their phylogenetic origin, their 

 embryological development and their main- 

 tenance in the adult. 



Morphology has relations with sciences 

 quite outside of biology. I have already 

 insisted that the problems of form and 

 structure are also physiological problems, 

 but in last analysis they are, I think, prob- 

 lems of physics and chemistry. For my- 

 self, I have no doubt that we shall some 

 day be able to prove that each character- 

 istic of an organism depends upon a spe- 

 cific substance in the germ cell, and we may 

 hope by altering this substance experiment- 

 ally to change the corresponding charac- 

 teristic. Such a change is mutation and 

 mutation in last analysis, as de Vries main- 

 tains, depends upon external conditions. 



Apart from this it is certain that the 

 physiological processes involved in the in- 

 dividual's characteristics are modifiable 

 and, indeed, controlled by physical agents 

 in the environment. Thus it has been pos- 

 sible to show that certain salts play special 

 roles in the development of particular or- 

 gans or characteristics (Herbst). Loeb, 

 indeed, has shown that regeneraition of 



