EEVIEW OF GENUS ARGULUS — MEEHEAN 473 



The basal segment has broken and the suction cup is exposed, although 

 the remaining segments are still intact. The suction cup is exactly 

 the same as that of the adult except that the number of segments in 

 the chitinous ribs supporting the margin is smaller. Each rib is 

 composed of one long and two short segments, with the distal one 

 only faintly defined. The basal segments of the second maxillae have 

 two long setae in the middle of the posterior margin of the scaled 

 area besides many scales on the surface. 



The branches of the stomach have become fairly complex. On the 

 first thoracic leg the rudimentary flagellum has two setae while that 

 on the second leg has one. On the ventral posterior edges of the 

 coxa of the second leg of the male the bilobed prominence is laid 

 down. On the third leg the socket is indicated by two lateral folds 

 and a projection on the ventral side that will become the median fold. 

 The precoxa and coxa of each leg have small spinules or scales on 

 the ventral side. The abdominal lobes have grown considerably and 

 the anal sinus reaches about one-fourth the length of the abdomen. 



Sixth stage. — The difference between the fifth, sixth, and seventh 

 larval stages is found in the residual portion of the first maxillae 

 and in the degree of development of the male accessory copulatory 

 apparatus. These stages cannot be distinguished in the female 

 because of the great variation in the size. 



They have attained a length of 1.6 to 2.0 mm. The residuum of 

 the first maxillae shows no segmentation. On the second and third 

 legs the accessory apparatus is the same, but a rounded prominence 

 has made its appearance on the anterior distal corner of the basis 

 of the fourth leg where the peg of the male will be located. The 

 abdominal processes are faintly defined at the base of the abdomen 

 in the female. 



Seventh stage. — The sixth and seventh stages are attained in 10 

 to 18 days. At this time the animal has reached a length of 2.0 to 

 2.2 mm. The lobes of the carapace have extended to cover the third 

 legs, and the dorsal ribs are distinctly forked. On the first maxillae 

 the residual degenerating portion consists of a small process pro- 

 vided with a minute spinule, while the ribs of the suction cups have 

 added a short segment. 



On the first two swimming legs the flagella have become longer 

 and reach beyond the proximal margin of the basis. They are pro- 

 vided with several plumose setae. On the male the bilobed protu- 

 berances of the coxae of the second legs are fairly conspicuous, and 

 the socket of the third pair is almost complete, although the papil- 

 lated processes in front of the aperture are not yet apparent. On 

 the fourth leg the peg is almost like that of the adult. It is pro- 

 vided with a lobed process on the ventral side, and the tip ends in 



