Dr. A. Krohn on the Development of the Cirripedia. 427 
rudiments of the compound eyes appeared more crowded together 
and of a darker or blackish colour. The swimming feet had 
become further developed. On the morning of the fourth day 
I found the animal already metamorphosed, which, as was to 
be expected, did not take place without a shedding of the pre- 
vious envelopes of the larva. 
Although these observations evidently proved that in the 
transition to the second period of development the carapace be- 
comes converted into the bivalve shell, and the whole anterior 
portion of the caudiform appendage into the thorax, it still 
remained quite uncertain from what parts the ambulatory or 
adhesive feet might have been produced. I only obtained accu- 
rate information upon this point subsequently in Messina, from 
the larva of another nearly allied species, which was captured 
in a very far advanced stage, and the metamorphosis of which 
took place as early as the evening of the same day. From this 
larva, in the compound eyes of which the individual crystalline 
bodies imbedded in the pigment-mass were distinctly recogniz- 
able, I believe I have ascertained with certainty that the adhe- 
sive legs are produced from the anterior pair of swimming feet 
{in the first stage of the larva]. The end of each of these feet 
was flattened into a disk, upon which a terminal joint appeared 
to be seated, exactly in the same way as in the adhesive feet*. 
Judging from the above results, the larva of a Lepas observed 
by Burmeister (/. c. p. 16, tab. 1. figs. 3 & 4), and regarded both 
by that naturalist and by Darwin (/. c. p. 109) as the represen- 
tative of a stage of development immediately preceding the 
Cypris-form, can no longer be taken as such. It is already, as 
shown by Burmeister’s figure, attached by means of the adhesive 
feet, and possesses a bivalved shell, but differs essentially [from 
the ordinary form] in having, instead of six, only three pairs of 
swimming feet, of which the foremost is stated to be undivided. 
I can consequently regard this larva as nothing but an aborted, 
or, which is more probable, as a monstrous specimen. 
In conclusion, I may call attention to a young Cirripede- 
larva observed in Messina, probably belonging to a Lepadide. 
The carapace, as shown in fig. 2, is pentagonal, and armed on 
the upper surface with a strong spine, the apex of which is bent 
backwards, and on the margins with several symmetrical longer 
* The opinion of Burmeister and Darwin, that the horns of the carapace 
become metamorphosed into the adhesive feet (“ prehensile antenne ” of 
Darwin), is consequently erroneous. The horns, as I convinced myself, 
are thrown off unchanged with the envelope of the larva. What becomes 
of the two posterior pairs of swimming feet in the change is entirely un- 
known to me. 
28* 
