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 antennae 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* 



