XII 



BACKBONELESS ANIMALS 



221 



clear water of brooks, by the limy-shelled, chalk-forming 

 Foraminifera which move slowly on seaweeds or at the 

 bottom of shallow water, or in some cases float at the 



': ^j fV '.?':**" .'.'*-".""-.'.: 



' /' " " '.". -*^."."-_ '. :''. 



+ -'* . r ' 



Y'"/' = x--^"' / M 



\ A....;-- / / = / i 



FIG. 60. A DIAGRAM SHOWING THE STRUCTURE OF Noctiluca miliaris. 



THE COMMONEST CAUSE OF " PHOSPHORESCENCE " IN THE SEA. 



It is a flagellate Infusorian, one of the Cystoflagellata , and is enormous 

 for a flagellate, being about the size of a small pinhead (^ inch or so in 

 diameter). It is rather like a melon in shape. 



It drives itself through the water by means of a strong, cross-striated 

 flagellum (FL). There is a smaller flagellum (/I) that wafts food into the 

 mouth (M). The oval depression is continued inwards as a furrow with 

 a rod-like ridge (R). The protoplasm (P) is dense in the centre around the 

 nucleus (N), but very much vacuolated towards the periphery, where it 

 forms a continuous layer beneath the cuticle. The meshes of the proto- 

 plasmic network are filled with liquid. Some captured organisms are 

 shown in the central protoplasm, and it is there that the luminosity is 

 most condensed. 



surface of the sea, and by the flinty-shelled Radiolarians 

 which live in the open ocean. In all these the living 



