ANELASMA SQUALICOLA. 173 



split during continued growth being thus exhibited : those 

 in the uppermost part almost symmetrically surround the 

 peduncle, showing that here, as in other Lepadidse, has 

 been one regular line of growth ; but in the lower part 

 the lines are extremely irregular; and what is almost 

 unique, it appears that the blunt basal end is constantly 

 increasing in length and breadth, and, apparently, at a 

 greater rate than any other part. I judge of this latter 

 fact, from the whole bottom of the peduncle being covered 

 with numerous curved, or nearly circular, lines of natural 

 splitting, the nature of which can be best understood 

 by examining the much-enlarged drawing (PL IV, fig. 3) 

 of a small portion (taken by chance) of the membrane 

 of the base, seen from the outside, and bearing some of 

 the simplest branched filaments : other branches, as may 

 be seen, have been cut off. This manner of growth ex- 

 plains the broad, blunt basal termination of the peduncle, 

 so unlike that in other Lepadidse. New membrane is 

 formed, not continuously as in other cases, under the 

 whole surface of the old membrane, but in irregular 

 patches ; thus the portion marked (a) runs under (b), but 

 not under the little circles (<?, c), for these are the last- 

 formed portions and underlie the membrane (a) and (5). I 

 do not understand how the splitting of the old membrane 

 is effected ; but no doubt it is by the same process by which 

 the membrane of the capitulum in other genera, as in 

 Scalpellum, splits symmetrically between the several 

 valves. In the branched filaments it is particularly dif- 

 ficult to understand their growth, for it is not possible, 

 after examining them, to doubt that they continue to 

 increase, and send off sub-branches, which it would 

 appear probable, penetrate the shark's flesh like roots. 

 I may remark that one, or more commonly two or three 

 branched filaments stand nearly in the centre of each 

 circular line of exuviation or splitting. The branched 

 filaments first commence as mere little pustules, and 

 these appear to be most numerous at the bottom of the 

 peduncle. 



