22 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



Cyclops and follow its life history as described by Dietrich (1915) 

 and by Ziegelmayer (1925). 



The Cyclops larva hatches from the egg as a typical nauplius (figs. 

 7 A, 8 A), which is followed by a second nauplius instar and four 

 metanaupliar instars (fig. 8 B, C, D, E) in which the body lengthens, 

 and finally (E) five pairs of appendages are added beyond the mandi- 

 bles, including the maxillipeds (Mxpd) and two pairs of legs (/L, 



Fig. 7. — Copepoda. Nauplius and two metanaupliar instars of Cyclops (outlines 

 from Ziegelmayer, 1925). 

 A, nauplius, ventral, showing three pairs of appendages and labrum {Lni). 

 B, first metanaupliar instar. C, fourth metanaupliar instar. 



2L). At the next moult the larva (F) begins to take on the form and 

 structure of the adult (G) and is now termed a copepodid, the ending 

 id signifying that at this stage the larva has become copepodlike. The 

 first copepodid acquires a third pair of legs ; with further growth it 

 passes through six copepodid instars until at last it becomes a sexually 

 mature adult (G). Among Cyclops species there is thus no abrupt 

 change between the various stages of growth, but new segments are 

 added and the appendages develop from simple rudiments to their 

 definitive forms. According to Ziegelmayer the segments formed 

 after the nauplius stage are generated in a subterminal zone of growth. 



