16 MORPHOLOGICAL DEVELOPMENT. 



of elongation in various types; and that in each kingdom 

 acquisition of the common trait has had a tendency now to 

 obscure morphological equivalence, and now to give the ap- 

 pearance of kinship where there is none. A further pur- 

 pose has been to prepare the way for a question hereafter 

 to be discussed whether, in the various types of either king- 

 dom, the elongation is effected in the same ways or in dif- 

 ferent ways. We shall have to ask whether the vertically 

 growing part is always, like that of Lessonia, a simple in- 

 dividual, or whether, as possibly in Phasnogams, it is a united 

 series of individuals; and similarly whether the elongated 

 body is always single, like that of a mollusc, or whether, as 

 possibly in annulose animals, it is a series of united in- 

 dividuals.] 



