3238 THE JOINTED ANIMALS 



this family belongs the genus Leucfier, remarkable for having the eyes and antennae 

 supported at the end of a long neck which extends in advance of the mouth. The 

 gills are absent, respiration being effected by means of the general integument, 

 which is so thin that the internal organs can be seen. In the figure the dark line 

 (n) is the ventral nerve chord which throws out finer branches from ganglionic 

 swellings in each of the segments; (h) is the heart, while immediately below the 

 latter is the stomach, passing forward into the gullet and backward into the intestine. 



CLEFT-FOOTED GROUP Order SCHIZOPODA 



This name is applied to a group nearly allied to the long-tailed Decapods; the 

 chief difference between them being in the fact that in the present order the eight 

 thoracic limbs are similar in structure, each being pediform and provided with a dis- 

 tinct exopodite on the second segment. The gills, which are attached either to the 

 thoracic or abdominal appendages, generally project into the water, and are but 

 rarely concealed in a chamber. The eggs are carried by the female beneath the 

 trunk, and are frequently protected 'by the development of a pouch. The order 

 contains several families embracing a large number of mostly marine forms, some 

 of which occur at great depths. Of the British species, the finest is Nyctiphanes 

 norvegica, which forms an important part of the food of herrings. It has luminous 

 organs on the thorax and abdomen, and when swimming in a glass vessel, in a dark- 

 ened room, appears like a flash of light. The young, as in all the members of the 

 family Euphausiidce, are hatched in the Nauplius stage. Most Schizopods are 

 small, but species belonging to the genera Lophogaster and Gnathophausia measur- 

 ing as much as six inches in length have been obtained. To the family Mysidce 

 belongs the genus Mysis, or opossum shrimps, among which is M. veheta from cer- 

 tain lakes in Northern Europe. Into these lakes the species is presumed to have 

 entered while they were connected with the sea; a supposition borne out by the 

 fact that it is nearly related to M. oculata, now living in the Arctic Ocean. 



THE MANTIS SHRIMPS Order STOMATOPODA 



The mantis shrimps (Sqwttidai) y which owe their name to the resemblance 

 that their seizing limbs bear to those of the insect mantis, are abundant in tropical 

 seas, where they sometimes reach a large size. Although bearing a general likeness 

 to the long-tailed Decapods, they may be recognized by certain prominent character- 

 istics. A ^"glance at the illustration will show that the carapace is so short 

 as to leave the hinder segments of the thorax uncovered, and, since the gills are 

 attached to the abdominal limbs, it forms no branchial chamber. Only three 

 pairs of limbs are modified into jaws, these being the mandibles and two pairs of 

 maxillae. The remaining eight pairs of thoracic limbs are foot-like, the large 

 prehensorial pair corresponding to the second maxillipedes of a Decapod. Two 

 kinds of mantis shrimp are occasionally met with in the English Channel, namely, 

 Sq-uilla desmaresti and S. mantis. The former is not uncommon along the shallower 



