674 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxv. 



able in the first maxillipeds where the sucking disks are gradually 

 developed at the expense of the terminal segments and barbed hooks 

 (fig. 11). 



The sexual organs have been completed by the development of an 

 oviduct in the female leading back to the sinus between the posterior 

 lobes on the last pair of legs, and by the completion of the vasre effer- 

 entite and the formation of ejaculator}^ ducts in the male. With the 

 fourth molt the copulatory organs begin to show themselves on the 

 legs of the male, and the sucking disks become capable of functioning 

 as organs of attachment. Hence we must regard the larval stage as 

 finished and the fifth period as the beginning of adult life. Subse- 

 quent molts follow at intervals of three or four da3^s until, at the end 

 of four weeks, the }■ oung Argulids become sexuall}^ ripe and the males 

 are capable of the complicated process of copulation. They are now 

 from 2.5 mm. to 3 mm. in length, and Claus states that in A.foUacem 

 the females must reach a length of at least 7 mm. before becoming- 

 ready for their first ^gg laying. 



SUMMARY. 



1. The female Arguli do not carrv their eggs about with them, but 

 deposit them in rows upon stones or other convenient hard surfaces 

 and leave them to care for themselves. 



2. The eggs are ellipsoidal in form, 0.35 to 0.1:5 mm. in length, and 

 are placed end to end in the rows. They are covered with a gelati- 

 nous envelope, which swells and hardens on contact with water, fasten- 

 ing the eggs securely to the surface and to one another. 



3. In the period of incubation the Arguli separate into three groups, 

 one of which, represented ])y the two fresh-water forms, foliaceus^n^ 

 catostomi, requires thirty to thirtj^-five days before hatching. A sec- 

 ond group, represented by the fresh-water form americamis, requires 

 but fifteen to eighteen da3^s, while the third group, represented Iw the 

 fresh-water stlsostethii and the salt-water megalops^ remain in the ^gg 

 from sixtv to eighty days. 



1. The emerging larvte separate themselves into two groups corre- 

 sponding, respectively, to the three short and the two long periods of 

 incubation. 



In the group which hatches in a month or less the nauplius, meta- 

 nauplius, and early cyclops stages are passed inside the %gg and the 

 larva emerges in a later cyclops stage with all the appendages present, 

 but many of them in a very rudimentary stage of development. Loco- 

 motion is effected by means of the second antennae and a temporary 

 pair of mandibular palps, both of which are elongated and tipped with 

 long rowing setffi. Only the first pair of legs is at all developed, 

 the others being mere immovable stumps. The first maxillipeds are 

 not modified into sucking disks, but terminate in stout barbed hooks. 



