492 CIRRIPEDIA. 



peds of the male (fig. 230 E, pm*) separate again ; while in the female (fig. 

 230 D) they remain fused and develop a sucker. The male is only about 

 one-fifth the length of the female. In both sexes the abdomen is much 

 reduced. 



In the genera Anchorella, Lernaeopoda, Brachiella and Hessia, Ed. van 

 Beneden (No. 506) has shewn that the embryo, although it passes through 

 a crypto-Nauplius stage in the egg, is when hatched already in the Cyclops 

 stage. 



Branchiura. The peculiar parasite Argulus, the affinities of which 

 with the Copepoda have been demonstrated by Claus (No. 511), is hatched 

 in a Cyclops stage, and has no Nauplius stage. At the time of hatching it 

 closely resembles the adult in general form. Its appendages are however 

 very nearly those of a typical larval Copepod. The body is composed of 

 a cephalo-thorax and free region behind this. The cephalo-thorax bears 

 on its under surface antennas (two pairs), mandibles, maxillipeds, and the 

 first pair of thoracic feet. 



The first pair of antennae is three-jointed, but the basal joint bears a 

 hook. The second pair is biramous, the inner ramus terminating in a hook. 

 The mandible is palped, but the palp is completely separated from the 

 cutting blade 1 . The maxilla would, according to Claus, appear to be 

 absent. 



The two typical divisions of the Copepod maxillipeds are present, viz. an 

 outer and anterior larger division, and an inner and posterior smaller one. 

 The first pair of thoracic feet, as is usual amongst Copepoda, is attached 

 to the cephalo-thorax. It has not the typical biramous Copepod character. 

 There are four free segments behind the cephalo-thorax, the last of which 

 ends in a fork. Three of them bear appendages, which are rudimentary in 

 this early larval stage. On the dorsal surface are present paired eyes as 

 well as an unpaired median eye. 



Between the larval condition and that of the adult a number of ecdyses 

 intervene. 



CIRRIPEDIA. 



The larvae of all the Cirripedia, with one or two exceptions, 

 leave the egg in the Nauplius condition. The Nauplii differ 

 somewhat in the separate groups, and the post-nauplial stages 

 vary not inconsiderably. 



It will be most convenient to treat successively the larval 



1 It seems not impossible that the appendage regarded by Claus as the mandibular 

 palp may really represent the maxilla, which would otherwise seem to be absent. 

 This mode of interpretation would bring the appendages of Argulus into a much 

 closer agreement with those of the parasitic Copepoda. It does not seem incompatible 

 with the existence of the stylet- like maxillce detected by Claus in the adult. 



