METAMORPHOSES OP CIRRIPEDES. 123 



this age there is no trace of the vesiculae seminales, so 

 conspicuous in the mature Cirripede. 



Young Cirripede, whilst within the pupa. — I repeatedly 

 succeeded in dissecting the young Lepas australis out 

 of the pupa ; and by the previous action of boiling potash, 

 and by a strong light, I was enabled to make a camera 

 sketch (PL 30, fig. 2) of the relative positions of their 

 several parts. The young Cirripede is drawn very faintly, 

 and is best seen by holding the plate in the same position 

 with the mature animal, of which a section is given in 

 my volume on the Lepadidse, PL 9, fig. 4. I may just 

 notice how complicated are the membranes in a longitudinal 

 section taken at this period : we have, 1st, beginning at 

 the back, the horny tissue of the carapace or bivalve shell 

 of the pupa ; 2d, the primordial valve {z, in fig. 3) of the 

 young Cirripede ; 3d and 4th, two folds of corium ; 5th, 

 the membrane of the sack of the Cirripede ; 6th, the mem- 

 brane of the sack of the pupa ; 7th, the outer tunic of the 

 thorax of the pupa ; 8th, the outer tunic of the thorax of 

 the young Cirripede ; 9th, the corium lining the latter 

 membrane ; and these nine membranes would be repeated 

 on the opposite side of the section, if it were taken through 

 either side of the shell or carapace, bordering the orifice. 



After the exuviation of the outer membranes of the pupa, 

 certain pre-existing coloured marks in the corium, such as 

 those round the eyes and round the acoustic orifices, along 

 the ridge of the back and on the borders of the orifice, &c, 

 are still retained by the young Cirripede, either temporarily 

 or permanently ; so that the correspondence of part with part 

 of the external surface admits of no doubt. Moreover, the 

 three terminal segments of the antennae are invariably re- 

 tained by the young Cirripede, though in a functionless 

 condition, and into them the^outer membrane of the body, 

 and an important organ, viz., the cement-ducts are still 

 prolonged ; hence these prolongations must be considered as 

 aborted antennae. Again, we have seen that the mouth of 

 the young Cirripede is formed under the rudimentary mouth 

 of the pupa, with the new oesophagus, round the old oeso- 

 phagus, leading into the same alimentary canal. The twenty- 

 four extreme tips, likewise, of the six pairs of biramous 



