SUB-KINGDOM VI. BRYOZOA 



[OR POLYZOA]. 

 MOSS ANIMALS. 



BY R. KlEKPATRICK. 



IF the sea-weeds and shells cast up on the sea-shore be carefully examined, 

 some of these objects will probably be found overgrown by encrustations and 

 patches, which, viewed through a lens, resemble fine lacework or tracery of 

 varying pattern. Probably, also, some of the supposed sea- weeds themselves 

 will, on closer inspection, prove to be wholly different from plants, and to 



be, in fact, Bryozoa. One of the commonest of 

 these plant-like animals is the Sea Mat or Broad- 

 leaved Hornwrack (Flustra foliacea), (Fig. 1), 

 found all round the shores of Great Britain, 

 growing in shallow water, 

 attached to shells and rocks. 

 It is often found in atun- 

 dance amongst the sea- 

 weeds cast up on shore, 

 especially after a gale. 



The Sea Mat forms thin 

 brown strap-shaped or fan- 

 shaped fronds, expanding 

 upwards from a flat, narrow 

 stem to a height of four to 

 six inches, and branching 

 A very fine reticuhte pattern is visible 

 Under a low magnifying power this 

 appearance (Fig. 2) is seen to be due to the raised 

 margins of oblong boxes arranged in longitudinal rows ; 

 two spines rise from the margin on each side of the 

 rounded and expanded upper end, and frequently 

 a fifth spine between and above the lateral pairs. 

 The front of each box is covered with a roof of mem- 

 brane. On examining a fresh leaflet in sea-water, 

 crowns of very slender tentacles will be seen to be 

 extruded through the upper ends of the front of the 

 boxes, a thin, horny, semi-circular lid being pushed up 

 during the process ; on the slightest alarm the ten- 

 tacles are rapidly withdrawn. It is also possible to see a bent tube beneath 

 the membranous roof. Each box or cell (Fig. 2) is the home of a polypide, 

 which has formed the cell. The tentacles of the polypide arise in a circle 

 from a platform, in the centre of which is an orifice, the mouth. 



665 



Fig. 1. FLUBTRA FOLIACEA. 



in one plane, 

 on both surfaces. 



Fig. 2. FLUSTRA (magni- 

 fied), showing polypiuea. 



a, Horny lid. 



b, Avicularium. 



c, Egg capsule. 



