ACTIONS OF AVICULARIA 485 



thin, chitinous " seta," which from time to time moves through the 



rater. The part of the vibraculum which represents the zooecium 



commonly bears a tubular rootlet, used for attaching the colony 



I to the substance on which it is growing (Fig. 254, p. 517). 

 In Microporella ciliata (Fig. 241, A) the avicularia are very 

 variable, and in some cases take on a " vibraculoid " character. 

 But in the fully-developed vibraculum (Fig. 242) there is usually 

 no such compromise of characters. It may, however, be noted 

 that Scricpocellaria scabra (Fig. 254), which belongs to a genus 

 characterised by its highly differentiated vibracula, possesses 

 structures (v.z) which could hardly be distinguished from avicu- 

 laria were it not for the presence of the rootlet (r). 



In the course of some observations which I had the oppor- 

 tunity of making on Bugula calathus at Naples, a fine hair offered 

 to a small colony was seized with such force by the avicularia 

 that the entire colony was lifted out of the water by the hair. 

 The same colony had captured (1) a small Nereis, which it held 

 with several of its avicularia ; (2) an Anisopod Crustacean, 2^ 

 mm. long; and (3) a small Amphipod, which was held by one of 

 its antennae. The Anisopod was held by the tip of one leg with 

 one avicularium, and by the penultimate joint of one of its chelae 

 with an avicularium of another branch. It was captured in such 

 a way that its chela, the " hand " of which was about half as long 

 as the avicularium, actually closed on to the avicularium without 

 being able to effect its escape. A little later the other chela was 

 caught by another avicularium. Curiously enough, however, an 

 avicularium did not necessarily close even when part of a captured 

 animal was actually in its mouth. The avicularia made no 

 attempt to place themselves in an advantageous position for 

 catching fresh parts of the Nereis, which they might easily have 

 done. The avicularia which had captured prey remained motion- 

 less. The others moved backwards and forwards (cf. the various 

 positions of the avicularia shown in Fig. 240) ten times in |- to 

 1 minute, snapping their jaws perhaps once in that time. The 

 two Crustacea were still retained by the avicularia two days 

 later. On the next day they had both disappeared ; but the 

 colony had again caught the Nereis, which had previously effected 

 its escape with the loss of nearly all its tentacular cirri. 



These observations, and others which have been recorded, do 

 not, unfortunately, give any information as to the purpose of the 



