xvii FLUSTRA, FLUSTRELLA AND BUGULA 467 



suitable resting-place, it fixes itself and forms the starting-point 

 of a colony, the number of whose individuals is continually 

 increased by the production of buds at the growing edge. The 

 " avicularia " of this species will be alluded to later (see p. 482). 



F./oliacea has long been known to possess in the fresh state 

 a remarkable odour, which is described, according to the fancy 

 of the observer, as a strong odour of fish, or as the smell of 

 violets after a shower. Others have compared it to that of the 

 orange or verbena, or to that of a mixture of roses and geranium. 



Flustrella hispida, another of our commonest Polyzoa, which 

 may be found between tide-marks on the stalks of Fucus, con- 

 sists of a softish brown encrustation, about one-sixteenth of an 

 inch thick, covered by numerous spines. If examined undis- 

 turbed in a rock-pool, ox transferred to a glass of sea-water, the 

 brown mass will be seen to become surrounded by a delicate 

 bluish halo, which is about as thick as the encrusting mass 

 itself, and consists of the tentacles of the numerous individuals of 

 the colony. The microscope shows that each individual is pro- 

 vided with a circlet of some thirty or more long, delicate ten- 

 tacles, which together form a graceful funnel (as in Fig. 233). 

 At the bottom of the funnel is the mouth, to which Diatoms or 

 other minute organic particles are conveyed by the cilia which 

 fringe the tentacles. If the tentacles be touched with a needle, 

 the whole funnel is retracted with great rapidity, and in this 

 retracted condition we see no more than the body- walls of the 

 animals. After an interval the tips of the tentacles are 

 cautiously protruded; the tentacles are gradually pushed out, 

 at first in a close bundle, but finally separating from one another 

 to form the funnel which we have already noticed. 



There is hardly a more surprising spectacle in the whole 

 animal kingdom than a living fragment of the genus Bugula. 

 The colony grows in the shape of a small tree, whose height may 

 amount to several inches ; and is characterised, in many species, 

 by a spiral arrangement of the branches, which makes the genus 

 easy to recognise at first sight (Fig. 233, A). The stem and 

 branches are composed of a single layer of zooecia, arranged 

 two or more abreast. Each zooecium bears, on its outer side, 

 a most singular body termed an avicularium, from its resem- 

 blance to a bird's head. Imagine a minute eagle's head attached 

 by a short but flexible neck to the zooecium. Suppose further 



