16 



C4UIDE TO THE CORAL GALLERY. 



High Wall 



Case 



E. end of 



Gallery. 



Fig. 12. 



the water (in a tumbler). On being magnified, the speck is seen to 

 be a spherical sac uniformly dotted with green points and progressing 

 by a peculiar revolving movement. Frequently the sphere con- 

 tains several green " daughter " spheres, and these, again, " grand- 

 daughter " spheres. The wall <jf the sphere is composed of a layer 

 of cells (the separate green points), each provided with two flagella. 

 The cells are embedded in a common jelly, each cell in a separate 

 compartment, but connected with its neighbours by radiating strands. 

 The outer surface of the sphere is covered with a pellicle through 

 which the pairs of flagella penetrate, and the interior is filled with 

 fluid in which daughter colonies may often be seen revolving. In 

 addition to a nucleus and contractile vacuole, the body of each cell 

 contains green chlorophyll granules. The daughter colonies inside 

 the sphere escape in due time by rupture of the outer wail of the 



parent. Volvox is generally regarded by 

 botanists as a plant. 



Gonmmpectorale (Fig. 11b), a colonial 

 organism belonging to the same family 

 as Volvox, forms flat plate-like colonies 

 composed of sixteen cells, each cell 

 having a pair of flagella at its upper 

 end. In one large section of Flagellata 

 the cell is provided at its upper end 

 with a collar, so the flagellum appears 

 to arise from the floor of a basin. 

 Codosiga cynisca (Plate IXa. in the Case) 

 forms a branching colony. Some of the 

 collared Flagellates secrete a horny cup or receptacle for the cell, 

 as in the solitary Salpingmca napiformis (Plate IXa. in the Case), 

 which forms a stalked horny cup containing the collared flagellate 

 cell. Proterospongia liaecJxli is a colonial form with Ama'ha-\i\Q 

 cells in addition to collared cells, all sunk in a common test. 

 The ancestor of the Sponges, which are unique among the Metazoa 

 in possessing collar-cells, was probably a collared Flagellate. The 

 MaU Coated Flagellata have a flattened body, with a longitudinal 

 groove from which a large flagellum projects, and usually, in addition, 

 a transverse groove with a flagellum lying in it. These forms are 

 mostly marine and often phosphorescent. Some species which have 

 a cuticular shell of cellulose, aud which contain chlorophyll, are 

 claimed by botanists as plants, but there are closely allied species 

 without the cellulose investment or the chlorophyll. O'eratium tripos 



Noctiluca miliaris, tlie Phos- 

 phorescent Animalcule. Mag- 

 nified 150 diameters. 



