X 



PHYLUM ARTHROPODA 



577 



permanently attached like the degenerate forms jusi described, but crawling 

 freely over the surface of the host. The body consists of an oval flattened 

 cephalo-thorax, and a small bilobed abdomen (&.). The mandibles and maxilla; 

 are piercing organs enclosed in a sucking-tube or proboscis (r. ), in front of which 

 is a median tube ending in a spine (*.). The second maxilhe are divided into 

 two portions, the anterior of which (kf.l) are modified into sucking-discs by 



FIG. 453. Argulus foliaceus, young male, a], antennule ; . 2 , Antenna; ab. abdomen; 

 b 6 4 , thoracic feet ; d. digestive glands connected with intestine ; kfl, anterior or suctorial 

 feet ; A/-', posterior or leg-like portion of second niaxilht' ; 2"<- paired eye ; /. rostrum : ml. shell- 

 gland ; st. stylet ; ts. testis ; uu, median eye. (From Lang's Comparative Anatomy-) 



which the parasite clings to the surface of its host, and there are four pairs of 

 swimming-feet (bl b4). Alone among the Copepoda the Branchiura have no 

 egg-sacs, and they are exceptional also in the possession of compound eyes (pa. ). 



The most familiar examples of the Eucirripedia are the Barnacles 

 found on ships' bottoms, piles, &c., and the Acorn-shells or Sessile 

 Barnacles, which occurin immense numbers on rocks between tide- 

 marks in all parts of the world. 



The common Barnacle (Lepas anatifcra) is attached by a long 

 stalk or peduncle (Fig. 454. A,|>), covered with a wrinkled skin, and 

 bearing at its distal end the body proper enclosed in a sort of 



