96 LEPAS FASCICULARIS. 



believe no cement tissue continues to pass out through these 

 lower apertures. Beneath the lowest aperture the two 

 ducts run into the two prehensile antennae of the larva, 

 which, as usual, terminate the peduncle. The antennae are 

 attached to some small foreign body in the centre of the 

 vesicular ball, by the usual tough, light brown, transpa- 

 rent cement. The two upper apertures are nearly on a 

 level with the outside surface of the ball; and it was 

 evident that as the animal grows, new apertures are 

 formed higher and higher up on the sides of the peduncle, 

 and that out of these, fresh vesicular membrane pro- 

 ceeds, and grows over the old ball in a continuous layer. 

 It appears that the growth of the vesicular ball is not 

 regular, — that it is not always formed, — and that when 

 formed the whole, or the lower part, sometimes disin- 

 tegrates and is washed away. As that portion of the 

 peduncle which is enclosed ceases to grow, and has its 

 muscles absorbed, retaining only the underlying corium, 

 whereas the upper unenclosed portion, and likewise, (as it 

 appears) lower portions once enclosed but since denuded, 

 continue to increase in diameter, the peduncle, when the 

 vesicular ball is removed, often has the most irregular 

 outline, contracting suddenly into a mere thread, and 

 then occasionally expanding again at the basal point. 



Frequently two or three specimens have their peduncles 

 imbedded in one common ball, of which there is a fine 

 specimen in the College of Surgeons (PL I, fig. 6), the 

 ball being about one inch and a quarter in diameter, 

 with a slice cut off. In this specimen, it is seen that the 

 vesicular membrane proceeding from several individuals, 

 unites to form one more or less svmmetrical whole, and 

 that the original common object of attachment is entirely 

 hidden. Dr. Coates* gives a curious account of the infi- 

 nite number of specimens, through which he sailed during 

 several days, in the Southern Atlantic Ocean : the balls 

 appeared like bird's eggs, and were mistaken for some 



* Journal of the Acad. Nat. Sc, Philadelphia, vol. vi, p. 138, 1829. 



