664 



PROCEEDINGS OF THE NATIONAL MVSEVM. 



joint being A'ery large and flat, furnished with large sickle-shaped 

 hooks on its lateral, and smaller ones on its anterior, margin, and evi- 

 dently functioning as an organ of prehension. 



The two terminal joints are small and armed with delicate tactile 

 bristles, and they just as evidently function as tactile organs. On the 

 bases of both pairs of antennie in all the larva^ are found stout spines 

 directed backward as in the adult (tig. 4). 



In the larvse of the first group the second antennte are very dif- 

 ferent in form from those of the adult, and serve as one of the two 

 principal locomotor organs. They ar-e very much elongated, extend- 

 ing far beyond the carapace, 

 and are made up of three 

 parts, a i^-jointed l)asipod 

 arising just posterior to the 

 eyes, each joint being armed 

 with a short spine, a stout 

 ondopod also 2-jointed and 

 tipped with a curved spine, 

 and a 1-jointed exopod bear- 

 ing at its tip four long plu- 

 mose seta? and a short thumb- 

 like one on the inner side. 

 These seta^ can be approxi- 

 mated or separated at pleas- 

 ure (Hg. 5). 



In contrast with these the 

 second antennse of the mega- 

 lop)< and dlzostethii larva? are 

 of ordinar3' length and con- 

 sist of a good-sized basal 

 joint extending back about 

 opposite the center of the 

 eyes, where it is armed near 

 the median line with the 

 usual blunt spine, a long 

 middle joint armed with two spines on its anterior surface, and a 

 short terminal joint tipped with a stout hook.' 



When straightened these antenna reach considerably beyond the 

 border of the carapace, but the latter nearly covers them when they 

 are partly folded, the position in which the larva usually carries them. 

 Hence they can not take any part in locomotion. 



Next in order posteriorly we find in our three larva? a pair of ap- 



FiG. 5.— Second antenna and labial palp of newly 



HATCHED LARVA OK ARGULUS FOLIACEVS (MODIFIED 

 FROM CLAUS). e.V., AND en., EXOPOD AND ENDOPOD OF 

 THE SECOND ANTENN>E; ll., HOOK CONNECTED WITH 

 BASE OF THE SAME; md. />., TEMPORARY MANDIBULAR 

 PALPS. 



iRellicott says that the second antenna; in stizostethii are four-jointed, but whether 

 he has again regarded the basal joint as double can not be decided either from his 

 figure or from the text. The probability is that he has, for the antennse in the 

 adults are like those of megalops. 



