THE SHAPES OF VEGETAL CELLS. 



177 



larly-conditioned on all sides, to a state in which two of their 

 opposite sides or ends are conditioned in ways that are like 

 one another, but unlike the ways in which all other sides are 

 conditioned. 



Still more instructive are the morphological differentia- 

 tions of those protophytes in which the first steps towards a 

 higher degree of integration are shown. In Fig. 10, represent- 

 ing one of the transitional forms of Desmidiacece, it is to be 

 noted that besides the difference between the transverse and 

 longitudinal dimensions, which the component units display 

 in common, the two end-units differ from the rest : they have 



«ffi*: 



y3& 



appendages which the rest have not. Once more, where the 

 integration is carried on in such ways as to produce not strings 

 but clusters, there arise contrasts and correspondences just 

 such as might be looked for. All the four members of the 

 group shown in Fig. 12, are similarly conditioned; and each 

 of them has a bilateral shape answering to its bilateral rela- 

 tions. In Fig. 14 we have a number of similarly-bilateral 

 individuals on the circumference, including a central in- 

 dividual differing from the rest by having the bilateral 

 character nearly obliterated. And then, in Fig. 15, we have 

 two central components of the group, deviating more deci- 

 dedly from those that surround them.* 



* One of my critics writes : — " This chapter might of course be enormously 

 extended, not only as in the preceding ones by citation of quite similar cases, 

 but by the introduction of fresh groups of cases." 



58 



