CRUSTACEANS. 609 



the stomach. These tubular glands are generally divided at the 



end near the mouth into a few blunt branches. Their precise 



connexion with the two main ducts has not been discovered. The 



state of these two masses varied much but since, at times, they 



contained aggregations of matter consisting of little balls closely 



resembling, in general appearance and size, the ovigerms with their 



germinal vesicles and spots, there could be no doubt that they are 



ovaria. DARWIN was unable to discover the orifice by which ST. 



ANGE supposes the ova to enter the sac. His observations lead 



Jiim to believe that the mode by which they enter the sac is quite 



; different : "Immediately before one of the periods of exuviation, 



the ova burst from the ovarian tubes in the peduncle and round the 



[pac, and, carried along the circulatory channels, are collected beneath 



I the chitine-tunic of the sac, in the corium, at this period remarkably 



[ spongy and full of cavities. The corium then forms, or rather, (as 



DARWIN believes,) resolves itself into a delicate membrane en velop- 



I ng each ovum and uniting them together in lamellae ; the corium, 



Laving thus far retreated, then forms under the lamellae the chitine- 



I;unic of the sac, and the last-formed one is immediately moulted 



vith the other integuments of the body. The membranes harden, 



he Iainella3 of ova become detached from the bottom of the sac, 



tnd are attached to the ovigerous frsena." In the Balanoidea the 



)ranching and inosculating ovarian coeca form a layer covering in 



>art the basis of the balanus, and in certain cases extending upwards 



>etween the two layers of corium round the walls of the shell 1 .] 



l?he testes lie on the sides of the body as small blind sacs that are 



ittached to branches that coalesce to form larger stems like veins. 



|)n each side there arises from the union of these branches a wide 



Ind tortuous canal (vas defer ens), which afterwards becoming nar- 



feower advances towards that of the opposite side; thus these two 



sltibes lie close together at the base of the caudiform appendage of the 



( ody, where they unite to form a ductus ejaculatorius, which opens at 



lie apex of the appendage 2 . In some lower crustaceans the females 



Ire much more numerous than the males, which are only imperfectly 



1 DARWIN Lepadidce, pp. 56 60, and Monogr. of the Balanida, London, 1854, 

 100. 



2 WAGNER in MUELLER'S Arcliiv, 1834, s. 467 473, Tab. vin. figs. 8 IT, 13; 

 'ARTIN ST. ANGE Mem. sur /'organisation dex Cirripedefi. Paris, 1835, 4*- PP- 



!, PL II. figS. 47. 



VOL. i. 39 



