THE CRUSTACEA 117 



race are also supposed to have belonged to them, but 

 of the species now living in British seas all are small 

 from microscopic dimensions to ha]f-an-inch in length, 

 and the latter size is reached by one or two species 

 only. 



They are divided into series according to their plan of 

 structure, the first of which is the Copepoda. The repre- 

 sentatives of this division have a segmented body, with the 

 anterior part covered with an oval shield, like the carapace 

 of the lobster, etc., a projecting jointed tail, and feet 

 adapted for swimming only. 



The common little Cyclops is always selected to figure as 

 the type. 



The Ostracoda have the body enclosed in a bivalve shell 

 (like the Cypris of the Cirripedes), and seven pairs of legs, 

 adapted for either swimming or walking. The body is not 

 segmented. 



The division termed the Caligidce includes the so-called 

 " Fish Lice." The curious and, under the microscope, 

 beautiful Argulus foliaceus of the pike, etc., is jjhe type. 

 An examination of any rough scaled sea fish, bass, wrasse 

 etc., will usually reveal a number of these. They are of 

 flattened form, oval, broad end in front, and run or glide 

 nimbly over the scales of their host. 



A species (if a true Entomostracan) the female of which 

 is the largest on our shores, is Chondr acanthus zei. It is 

 nearly always present on the gills of the " John Dory " 

 (Zeus faber), from which host its specific name is taken. 

 The male is microscopic. 



Some of the Entomostraca gleam with iridescent tints. This 

 feature is strongly marked in a large Copepod (Anomalocera 

 Pater sonii). A large foreign species (Sapphirina fulvescens) 

 is resplendent. 



The Copepods and Ostracods are abundant at the surface 

 of our seas, and on warm summer nights, when the surface 



