70 



SHELL GALLERY. 



Fig. 20. 



TuhuUpora flahellaris. 



a, half of an incrusting colony, x 8 ; h,& few cells, x 44 : c, a colony, 

 natural size. 



Table 

 Case A, 

 upright 

 part. 



Order II. — Phylactol^mata. 



All the forms in this group inhabit fresh water, where, in the 

 form of creeping or erect branching growths or masses, they grow 

 attached to fresh- water plants, tree-trunks, old wood, etc. ; two species 

 are capable of slow movement from place to place. The lophophore 

 and tentacular crown of the polypide are, with one exception, 

 horseshoe-shaped. The Order owes its name to the presence of a 

 lobe guarding the mouth. 



In addition to the sexual, there is an asexual reproduction by 

 means of peculiar internal buds termed statoblasts (Fig. 21). When 

 the colony dies in the autumn the liberated buds, securely protected 

 in a horny capsule, retain their vitality till the spring ; in due 

 season the valves of the statoblast burst open, and the contents 

 develope into a new colony. The statoblasts, which resemble small 

 seeds, are usually provided with a ring of air cells, which act as a 

 float, and in some species spines are present. 



