RELATIONS OF ANIMAL MORPHOLOGY 253 



bound together, for every form or part has not merely a form or 

 function, but a development, and development is a dynamical pro- 

 cess. A decade or two ago embryological development was regarded 

 as a purely morphological subject, as a series of stages, and little 

 attention was paid to the causes that produce the stages and the suc- 

 cession 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 totipotent, as in the medusse; in 

 other cases, the different parts of the cytoplasm seem told off to de- 

 velop into particular and definite organs, as in some mollusks. We 

 have learned, further, that at every stage new organs are called forth 

 and their development directed by stimuli proceeding from already 

 existing organs. 1 



Moreover, it has been found that even adult structures are depend- 

 ent upon external conditions for their form. It appears that peculiar 

 functioning may alter the form of internal organs, as has been de- 

 monstrated in the case of a ship's trimmer and of a cobbler by Lane, 2 

 and as a vast number of pathological cases testify, such as the altera- 

 tion of the arrangement of plates in the spongy tissue in the head of 

 the femur, 3 and the functional hypertrophy of the other kidney after 

 the loss of one. Morphologists have been forced to realize that form 

 and structure cannot be dealt with aside from function and behavior. 

 Every part of the living body is a sensitive, responding part whose 

 sensitiveness determines structure. This is seen particularly 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 animals) of the nervous system, 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 physiological realm. 



From these experiences I conclude that the morphologist who studies 

 form characteristics only is too narrow. Characteristics in their two- 



1 The literature on this subject is extensive; recent resume's are given in E. B. 

 Wilson's The Cell in Development and Inheritance, 2d ed., 1903 ; also, T. H. Morgan's 

 Regeneration, New York, 1902. Read also E. B. Wilson, The Problem of Develop- 

 ment, Science, xxi, 281-294, Feb. 24, 1905. 



2 Lane's papers were published in the English Journal of Anatomy and Physi- 

 ology, fifteen or twenty years ago. 



3 On the architecture of the spongy tissue of the head of the femur, see H. Meyer, 

 Archiv fur Anatomie u. Physiologic, 1869; J. Wolff, Virchow's Archiv fur pathol. 

 Anat. L (1870) and LXI (1874); also Roux, Gesammelte Abhandlungen, and Roux, 

 Der Kampf der Theile im Organismus, Leipzig, p. 27, 1881. 



