10 ' A PIECE OF HORN WRACK : 



tufts, with zooecia protected by six or seven long spines, and dis- 

 tinct round ovicells, form beautiful microscopic objects, especially 

 with a background of polarised light. 



The Cyclostomata delight in the fronds of Flustra as 

 habitats. Tufts of the '' Ivory-tufted Zoophyte," Crista ebur- 

 nia, Plate I., Fig. i (c); the "Goat's Horn CoraUine," C. 

 cornuta, Plate I., Fig. 5; and the "Black-jointed Coralline," C. 

 denticulata, Plate II., Fig. 6, may be found often on one frond of 

 Hornwrack. The Crisice are very beautiful zoophytes ; C. cornuta 

 is excedingly delicate, looking almost like white hairs tangled to- 

 gether, but under the lens appearing as " branches of single cells 

 shaped like goats' horns inverted, placed one above the other, on 

 the top of each of which is a small circular opening which inclines 

 inwards. At the back of this rises a fine upright hair, near the 

 insertion of the next cell above it." — Ellis (see Plate I., Fig. 5 a.). 

 The brittle C. ebuniia, or " Ivory-tufted zoophyte," is easily distin- 

 guishable by its brilliant white appearance, and no more beautiful 

 object can be seen under the condenser than a tuft of this species. 

 The cells are arranged in intervals with from three to nine cells in 

 each, and are tubular and covered with minute granulations. The 

 ovicels, which are often present, are pear-shaped and, like the 

 zooecia, are perfectly white,- and spotted with minute dots (see Plate 

 II., Fig. 7). In C. de7iticidata the internodes are longer, having a 

 much larger number of cells, and the joints between the internodes 

 are usually black. The last species is much duller in appearance 

 than C. eburnia, grows more erect and to a greater height, and is 

 more branched. I have recently found this species, as well as C. 

 cornuta, crowding the margins of rock pools on Filey Brigg. We 

 sometimes find (Plate I., Fig. i,d) on Flustra a small round white 

 wart-like polyzoon, with the base expanded slightly as a thin border. 

 Under the lens this is found to be a colony of tubular cells, ex- 

 tending from the centre outwards in radiating lines. The cells are 

 marked with minute dots. This is the " Wart-like Coralline " of 

 Couch, or Diastopora patina. 



Amongst the Ctenostomata, Bowerbankia imbricata (Plate 

 II., Fig. 8), is often found upon the Flustra. The cells are 

 arranged in groups upon a creeping stolon, and are horny and so 

 transparent that the structure of the polypide, and notably its 



