204 THE INDUCTIONS OF BIOLOGY. 



cation of one or more members of the polypedom into a 

 swimming apparatus, which, by its rhythmical contractions, 

 propels itself through the water, drawing the polypedom after 

 it. And in the more differentiated Physalin^ various organa 

 result from the metamorphosis of parts that are the homo- 

 logues of individual polypes. In this last instance, the in« 

 dividuality of the aggregate is so predominant, that the 

 individualities of the members are practically lost. This 



combination of individualities in such way as to produce a 

 composite individual, meets us in other forms among the 

 ascidian molluscs. While in some of these, as in the 

 Clavelina, the animals associated are but little subordinated 

 to the community they form ; in others, as in the Botryllidce, 

 they are so fused into a rounded mass, as to present the 

 appearance of a single animal with several mouths and 

 stomachs. 



On the hypothesis of Evolution, perplexities of this nature 

 are just such as we might anticipate. If Life in general, com- 

 menced with minute and simple forms, like those out of 

 which all individual organisms, however complex, now 

 originate ; and if the transitions from these primordial units 

 to organisms made up of groups of such units, and to higher 

 organisms made up of groups of such groups, took place by 

 degrees ; it is clear that individualities of the first and 

 simplest order, would merge gradually in those of a larger 

 and more complex order, and these again in others of an 

 order having still greater bulk and organization ; and that 

 hence it would be impossible to say where the lower indivi- 

 dualities ceased, and the higher individualities commenced. 



§ 73. To meet these difficulties, it has been proposed that 

 the whole product of a single fertilized germ, shall be re- 

 garded as a single individual : whether such whole product 

 be organized into one mass, or whether it be organized into 

 many masses, that are partially or completely separate. It 

 is urged that whether the development of the fertilized ^evm 



