105 



CHAPTER V. 



CONCLUDING REMARKS ON THE ALTERNATING GENERA- 

 TIONS AND THEIR REAL NATURE. 



The mode of development by means of "nurses" or 

 intermediate generations, is thus seen to be no longer an 

 isolated phenomenon in nature. The circmnstance of an 

 animal giving birth to a progeny permanently dissimilar 

 to its parent, but which itself produces a new generation, 

 which either itself or in its offspring, returns to the form 

 of the parent animal, is a phenomenon not confined to a 

 single class or series of animals ; the vertebrate class is 

 the only one in which it has not yet been observed,* It 

 would consequently appear that there is something in- 

 trinsic in this mode of development, and that it occurs as 

 it were with a certain necessity ; on which account it will 

 undoubtedly soon be recognized to a greater extent and 

 more generally. It should no longer be considered as 

 something paradoxical or anomalous (as we have hitherto 

 been too much inclined to deem both it and the pheno- 

 mena in which it is exhibited,) it must be in harmony with 

 the rest of development in nature, in which the funda- 

 mental principle of this com^se of development must also 

 be elsewhere expressed, although it may be displayed 

 in a form under which we shall less readily perceive and 

 recognize it. This is seen when we trace the mode of 



* To the instances adduced in the foregoing pages, we might add the 

 • eyclical development of the mrticellce, as it has been described by Ehrenberg. 



