6 MORPHOLOGICAL DEVELOPMENT. 



homologies of its different parts become problems. Undei 

 the disguises induced by the consolidation of primary, second- 

 ary, and tertiary units, it has to be ascertained which answer 

 to which, in their degrees of composition. 



Such questions are more intricate than they at first appear ; 

 since, besides the obscurities caused by progressive integration, 

 and those due to accompanying modifications of form, further 

 obscurities result from the variable growths of units of the 

 different orders. Just as an army may be augmented by re- 

 cruiting in each company, without increasing the number of 

 companies ; or may be augmented by making up the full 

 complement of companies in each regiment, while the 

 number of regiments remains the same; or may be aug- 

 mented by putting more regiments into each di\^sion, other 

 things being unchanged ; or may be augmented by adding to 

 the number of its divisions without altering the components of 

 each division ; or may be augmented by two or three of these 

 processes at once ; so, in organisms, increase of mass may be 

 due to growth in units of the first order, or in those of the 

 second order, or in those of still higher orders ; or it may be 

 due to simultaneous growth in units of several orders. 

 And this last mode of integration being the general mode, 

 puts difficulties in the way of analysis. Just as the structure 

 of an army would be made less easy to understand, if com- 

 panies often outgrew regiments, or regiments became larger 

 than brigades ; so these questions of morphological composi- 

 tion, are complicated by the indeterminate sizes of the units 

 of each kind — relativel3^-simple units frequently becoming 

 far more bulky than relatively -compound units. 



§ 177. The morphological problems of the second class, 

 are those having for their subject-matter the changes of shape 

 that accompany changes of aggregation. The most general 

 questions respecting the structure of an organism, having been 

 answered when it is ascertained of what units it is composed aa 

 a whole, and in its several parts ; there come the more special 



