EVIDENCE FROM COLONIAL OR COMPOUND ANIMALS. 287 



striking is it to find that a lobster's " feelers " really correspond in 

 nature with its legs ; that its eye-stalks agree with part of the append- 

 ages of its tail-joints, and that its jaws are simply the feet of the 

 head, so to speak, modified for chewing. These varied organs arise 

 from a common type, just as the joints which bear them exhibit a 

 singular uniformity of structure. Hence a lobster, or other Articulate 

 .animal, gains the best possible title to be named colonial, in that it 

 is not merely composed of visible " units," but also in that these 

 units are modifications of a common and single plan. In connection 

 with the curious phases of worm-growth observed in the Naidides 

 (Fig. 192), we may note that the individuals of the centipede-class 

 increase in size and add new segments to their bodies in a somewhat 



FIG. 194. DEVELOPMENT OF JULUS. 



similar fashion. When a young centipede or gally-worm (Julus) 

 (Fig. 194) is attaining its full growth, new joints are seen to bud out 

 between the last segment but one (C,/; D, n s) and the joints in 

 front thereof; so that the last-formed joints (E, 9-14) in a young 

 centipede are placed towards its tail-extremity. If we could imagine 

 that some of these last-formed segments developed a head, and 

 separated themselves from the parent-frame as a new being, we 

 should possess an exact imitation of the process whereby the young 

 Nai's (Fig. 192) originates from its parent-form. 



An interesting biological speculation has arisen in connection 

 with the personality of those familiar animals the Starfishes (Fig. 195). 

 Here we find a central body or disc (Fig. 195, i), with, in the common 

 species, five rays or arms, containing each an exactly similar arrange- 

 ment of the organs of the body, diverging therefrom. Haeckel's 



