706 William Patten 



But if a celi absorbs more matter than it has energy to transform , tUe 

 matter will remain statiouary uuless the necessary Stimulus is brouglit 

 from tliose cells which receive an excess of euergy, or Stimuli. But the 

 excess of energy in the one celi would not be lost , but transferred to 

 others near it, by mere contact. This would be the first step in the trans- 

 formation of indifferent cells, or those in which the entire sequence of 

 events called vitality is fulfilled, into those which perform only a part 

 of this process. As soon as an indifferent cell absorbs more 

 energy than is necessary forits own vital processes, itbe- 

 comes a dynamophagous, or sense celi. Those which absorb 

 more matter than is necessary for themselves become hylophagous. 

 The origin of thelatter is not so simple as that of the former, since it 

 was the result of two distinct processes: (1) the direct absorption of 

 matter by certain cells; and (2) the deposition in them, by the gene- 

 rating body, of matter, before they were capable of independentmotion. 

 To follo w these two processes is not at preseut our object, only in so 

 far as they bave to do with the origin of the sense cells. We bave said 

 that the transfer of energy from a dynamophagous celi to a hylopha- 

 gous one was, at first, by simple contact, and it follo ws that the two 

 cells must be developed side by side. Our supposition of an indepen- 

 deut group of indifferent cells was only to make our meaning clear, for 

 it is very probable that no such condition ever existed. We see in many 

 Protozoa a Constant differentiation of one pole from the other, so that 

 the so-called animai functions are confined to one end, and the vege- 

 tative to the other. According to the laws of di vision, or of segmen- 

 tation, such a bipolar cell would never give rise to a group of indifferent 

 ones, but to a bipolar body, the relation of the poles in the single celi, 

 and in the group of cells, remaining the same. Therefore, in the sim- 

 plest, multi-cellular animai, the cells are already differentiated , the 

 vegetative ones being confined to one pole, around which the energiz- 

 ing, or sense cells, would form a ring. This condition is realized in 

 the simplest Coelenterates. In the simplest condition, the distance be- 

 tween the organs receiving Stimuli and those giving them, or sense Or- 

 gans, is not great, so that the latter perform a double function: (1) 

 receive the Stimuli from without, and (2) conduct them to the necessary 

 centres. Such organs are very commonly found in the Coelenterates and 

 MoUuscs, and consist of slender cells with largo, basai, and nucleolated 

 nuclei, ending externally in sensory hairs and internally in long, sensi- 

 tive fibres (in Mollusca, usually a single one) whose exact method of 

 termination is unknown , but from theoretical reasons there can be but 



