CHAP. IX. CIRRIPEDIA AND RHIZOCEPHALA. 93 



tion and bristling of the natatory feet; 11 they are 

 especially distinguished from them by the possession of 

 a pair of composite eyes. Sometimes also traces of the 

 frontal horns seem to persist. 12 



As the Cirripedia and Khizocephala now in general 

 resemble each other far more than in their Nauplius- 

 state, this is also the case with the individual members 

 of each of the two orders. 



The pupEe in both orders attach themselves by means 

 of the adherent feet ; those of the Cirripedes to rocks, 

 shells, turtles, drift-wood, ships, &c., those of the 

 Rhizocephala to the abdomen of Crabs, Porcellance, and 

 Hermit Crabs. The carapace of the Cirripedes be- 

 comes converted, as is well-known, into a peculiar test, 

 on account of which they were formerly placed among 

 the Mollusca, and the natatory feet grow into long cirri, 

 which whirl nourishment towards the mouth, which is 

 now open. The Hhizocephala remain astomatous ; they 

 lose all their limbs completely, and appear as sausage- 

 like, sack-shaped or discoidal excrescences of their 

 host, filled with ova (figs. 59, 60) ; from the point of 



11 Compare the figure given by Darwin (Balanidse, PI. xxx. fig. 5) of 

 the first natatory foot of the pupa of Lepas austrulis, with that of 

 Lernseodiscus Porcellanse published in the 'Archivfiir Naturgeschichte ' 

 (1863, Taf. iii. fig. 5). The sole distinction, that in the latter there are 

 only 3 setae at the end of the outer branch, whilst in the Cirripedia 

 there are 4 on the first and 5 on the following natatory feet, may be 

 due to an error on my part. 



12 Darwin describes as "acoustic orifices" small apertures in the 

 shell of the pupse of the Cirripedia, which, frequently surrounded by a 

 border, are situated, in Lepas pecMnata, upon short, hornlike processes. 

 I feel scarcely any hesitation in regarding the apertures as those of the 

 " shell-glands," and the hornlike processes as remains of the frontal 

 horns. 



