232 



MANUAL OF ZOOLOGY 



SECT. 



sh. gl.). The larva nearly always leaves the egg as a 

 characteristic form called the Nauplius (Fig. 125), which 

 occurs also, though exceptionally, as a free-swimming stage 

 in the Malacostraca, the Nauplius stage in that sub-class 

 being usually passed through in the egg. The Nauplius is 



.nt.1 

 ant.S, 



i& 



FIG. 124. Apus glacialis, ventral aspect. abd.f. abdominal feet ; ant, /, anten- 

 nule ; ant. 2, antenna ; Ibr. labrum ; md. mandible ; mx. first maxilla ; m>. aper- 

 ture of oviduct ; s.f.pl. sub-frontal plate ; sh.gl. shell-gland ; th.f. thoracic feet ; 

 th.f.i, first thoracic foot. (After Bernard.) 



an oval unsegmented body with a median eye, and three 



pairs of short appendages provided terminally with long hairs. 



Most of the Entomostraca are free-swimming, and the 



majority of them, such as the Water-fleas (Fig. 126) and 



