Kellicott, A Contribution to the Theory of Growth. cgn 



Herr Prof. Dr. W. E. Kellicott (Baltimore) hält seinen 

 angekündigten Vortrag: 



A Contribution to the Theory of Growth. 



By Wm. E. Kellicott (Baltimore). 



Progress in the study of growth has been neither as rapid 

 nor as substantial as of processes of coordinate importance. Even 

 the definitions of what the idea of growth really incmdes vary 

 from the simple statement, on the one hand, that growth is only 

 the bare phenomenon of increase in volume or mass, to the ex- 

 tremely inclusive statement, on the other, that all formative 

 processes leading to a permanent change of form or structure 

 are to be regarded as growth processes. 



One circumstance tending to retard progress in this field is 

 the fact that among animals growth has been studied • chiefly 

 among the mammals, and here growth is determinate; 

 that is, the organism grows during a comparatively brief early 

 period of its existence to a fairly definite average size which is 

 then practically constant throughout the remaining and greater 

 part of its life. But this is a special condition which obtains 

 apparently only among the birds and mammals and a few of the 

 invertebrate groups. By far the most general form of growth 

 is that shown by the fishes, amphibians, and reptiles and most 

 of the great invertebrate groups where growth is indeter- 

 m i n a t e ; that is, as long as the organism lives and f eeds it 

 continues to grow, although perhaps very slowly in the older 

 individuals. 



Another retardative condition here has been the common 

 method of attempting the study and measurement of the growth 

 of the organism as a whole. For example, studies upon 

 the growth of the mammal have given us the facts regarding 

 the amount and rate of increase in weight or length (stature) of 

 the entire organism. Practically the only exceptions concern the 

 central nervous System the growth of which has been studied 

 separately. One would not now attempt thus to describe the 

 development or differentiation of the organism as a whole, with- 

 out considering its parts separately, and one ought not to attempt 

 thus to describe its growth. 



During the few moments at my disposal I wish to draw at- 

 tention to the significance of certain facts regarding the growth 

 of organs or parts, which indicate why the consideration of the 

 growth of the organism as measured by increase in total weight 

 or length gives little real indication of the true phenomena of 

 growth, among the higher organisms at any rate. 



My data were drawn from 315 examples of the Elasmo- 

 branch Mustelus, canis (Smooth Dogfish). These varied in total 



