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 Nai'dides 

 (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 



