n8 PRIMITIVE FORMS OF LIFE 



capable of liberating themselves and of leading an independent 

 life (Siphonophora) ; these we shall call denudes. 



In these associations the component parts at first enjoy 

 almost complete independence, which has led to their having 

 been considered as constituting a special kind of body, to which 

 the name of colony has been given in order to distinguish it from 

 ordinary organisms. It is assumed — on a purely arbitrary 

 basis — that the merid of each zoid and the zoid of each deme 

 preserves its own individuality, although the zoid and the 

 deme are themselves deprived of it. However, as in the 

 associations of plastids, the diversification of form and function 

 in the merids brings about an increasing solidarity in the zoid, 

 which, through every possible transition has led us to transfer 

 to them the idea of indivisibility and unity that we have 

 produced from our own consciousness, and which we have 

 transferred to the higher animals and plants themselves. 



In actual fact all the hydromerids forming a hydrozoid 

 preserve enough independence to invest them with the various 

 forms, each corresponding more or less to a particular function 

 (without that form, however, becoming indispensable) which 

 their position, the conditions of their nutrition, and the stimuli 

 to which they are exposed, determine. Contrary to the opinion 

 generally expressed in the meaningless phrase " the function 

 creates the organ ", which is often applied incorrectly and 

 misguidedly, just because it has no significance, the hydro- 

 merids among the Hydroids become modified quite inde- 

 pendently of any function. They then perform such actions 

 as their form and position allow, and this activity then becomes 

 a function of which each pseudo-individual is naturally the 

 organ. Thus, along with the normal merids, which preserve 

 their mouth, eat and digest, and which may be called 

 gastromerids, others are found which, since they are nourished 

 by the former, dispense altogether with a mouth. They are 

 able, however, to seize and palpate objects. These dactylomerids, 

 functioning like fishing-tentacles, take on a large variety of 

 forms. Others of the community, the acanthomerids , transform 

 themselves into defensive spikes, thanks to their horny 

 covering. Others, again, find themselves placed in such 

 conditions that the buds they produce rapidly develop germ 

 cells ; these are the gonomerids, the carriers of the gamomerids, 

 some of which are male and others female. A. de Ouatrefages 



