136 HISTOKY OF CRUSTACEA. CHAP. XII. 



nules, like those seen in the roots of the adult animal. 

 I have therefore supposed these appendages to be the 

 rudiments of the future roots. A perfectly similar 

 appendage, " a most delicate tube or ribbon," was 

 found by Darwin in free-swimming pupae of Lepas 

 australis on the last joints of the " prehensile antennae." 

 From the perfect accordance in their entire structure 

 shown by the pupae of the Khizocephala and Cirripedia, 

 there can be no doubt that the appendages of Sacculina 

 and Lepas, which are so like each other and spring from 

 the same spot, are homologous structures. 



Now in three species of Lepas, in Dichelaspis War- 

 wickii and in Scdlpellum Peronii, Darwin saw, on tear- 

 ing recently-affixed animals from their point or support, 

 that a long narrow band issued from the same point of 

 the antennae ; its end was torn away, and in Dichelaspis, 

 judging from its ragged appearance, it had attached 

 itself firmly to the support. From this it follows that 

 this appendage in Lepas australis can hardly be any- 

 thing but a young cement-duct. If, therefore, the 

 supposition that the appendages on the antennae of 

 the pupae of Khizocephala are young roots be cor- 

 rect, the roots of the Ehizocephala are homologous 

 with the cement-ducts of the Cirripedia. And this, 

 strange as it may appear at the first glance, seems to me 

 scarcely doubtful. It is true that the act of adhesion 

 of the Ehizocephala has never yet been observed, but it 

 is more than probable that they attach themselves, just 

 like the Cirripedia, by means of the antennae, and that 

 therefore the points of attachment in the two groups 



