SECT. VII. 



CRUSTACEA. 



205 



scope the cells are seen to pass alternately from one 

 colour to another. There is a little three-lobed body 

 between the eyes connected with the central nervous 

 system by a small nerve ; it contains several corpuscules, 

 which Professor Gegenbaur regards as the remains of 

 the single eye of the larva which undergoes many trans- 

 formations before it arrives at its adult form. 



According to Professor Gegenbaur, the Sapphirina 

 fulgens is a true Copepod and the Mediterranean Phyl- 

 losoina is a Decapod, although it has a lacunar blood 

 system. 



Some genera of the order Copepoda inhabit salt water, 

 others fresh, as the Cyclops quadricornis (fig. 150), which 

 abounds in the water 

 with which London 

 is supplied. 



The genus Cyclops 

 is a type of the 

 bristly-footed group, 

 distinguished by a 

 single compound eye 

 placed in the middle 

 of the forehead. The 

 head and thorax are 

 almost entirely co- 

 vered with an oval 

 j oint ed buckler, which 

 has an opening below 

 to let the bristly 

 limbs pass through 

 (fig. 150); and the 

 tail, which is five- 

 jointed, ends in two 

 plates furnished with 

 bristly plumes. It is traversed by the intestine, which 

 ends near its extremity. The brilliant little eye in front 



Fig. 150. Female Cyclops: a, body ; 6, tail ; c, an- 

 tenna ; d, antennule ; e, feet ; /, plumose setae of 

 tail ; B, tail, with extrnal egg-sacs ; c, D, E, F, G, 

 successive stages of development of young. 



