60 LEPADID^l. 



the frsena, but still adhered to the newly-formed chitine 

 tunic of the sack ; in these, the ova were so tender, that 

 they broke into pieces rather than be separated from the 

 membrane of the lamella, itself hardly perfectly deve- 

 loped, for pulpy cellular matter adhered outside some of 

 the ova. These and other facts are quite inexplicable on 

 any other view than that advanced. 



As the lamellae are formed without organic union 

 with the parent, they would be liable to be washed out 

 of the widely open sack of the Lepadidae, if they had 

 not been specially attached to the frcena. These fraena 

 consist of a pair of more or less semicircular folds of 

 skin, depending inside the sack, on each side of the point 

 of attachment of the body. The fraena are often of consi- 

 derable size, but in Ibla, they are very minute ; they are 

 formed of chitine tunic with underlying corium, like the 

 rest of the sack ; on their crests, there is a row, or a set 

 of circular groups, or a broad surface, covered, either 

 with minute, pointed, bead-like bodies mounted on long 

 hair-like footstalks, or with staff-formed bodies on very 

 short footstalks. I measured some of the bead-like bodies, 

 in Lepas anserifera, and they were -^-oVoth of an inch in 

 diameter, and the footstalks three or four times as long 

 as the elongated heads. These heads, of whatever shape 

 they may be, have an opaque, and, I believe, glandular 

 centre ; I could not make out with certainty an aperture 

 at their ends, but, I believe, such exists, and they seem to 

 secrete a substance, which hardens into a strong membrane, 

 serving to unite the crest of the fraenum to the edges of 

 the lamellae. In one case, this bit of membrane seemed 

 formed of a woven mass of threads. These little glan- 

 dular bodies, with the membrane formed by them, are 

 cast off at each exuviation, and new glands formed on the 

 crest of the fraenum underneath. In some species of 

 Pollicipes, (viz., P. cornucojria and elecjans^) the fraena, 

 though present and large, are functionless and destitute 

 of the glands : I believe, they exist in this same function- 

 less condition, and in rather a different position in the 



