INDIVIDUALITY. 247 



is a special modification of one or more members of the poly- 

 pcdom into a swimming apparatus which, by its rhythmical 

 contractions, propels itself through the water, drawing the 

 polypedom after it. And in the more differentiated Physalia 

 various organs result from the metamorphosis of parts 

 which are the homologues of individual polypes. In this 

 last instance, the individuality of the aggregate is so pre- 

 dominant that the individualities of its members are practi- 

 cally lost. This combination of individualities in such 

 way as to produce a composite individual, meets us in other 

 forms among the ascidians. While in some of these, as in 

 the Clavelina and in the Botnjllidce, the animals associated 

 are but little subordinated to the community they form, in 

 others they are so combined as to form a compound indi- 

 vidual. The pelagic ascidian Doliolum is an example. " Here 

 we find a large individual which swims by contractions of 

 circular muscular bands, carries a train of smaller individuals 

 attached to a long dorsal process of the test. These are 

 arranged in three rows: those constituting the lateral row 

 have wide mouths and no sexual organs or organs of locomo- 

 tion — they subserve the nutrition of the colony, a truth 

 which is illustrated by the fact that as soon as they are 

 properly developed the large individual (the mother) loses 

 her alimentary canal ; " while from the median row are 

 eventually derived the sexual zoids. 



On the h3^othesis of Evolution, perplexities of this nature 

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

 commenced with minute and simple forms, like those out of 

 which all 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 com- 

 plex order, and these again in others of an order having still 



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