Dr. A. Krohn on the Development of the Cirripedia. 423 
— LIL1.— Observations on the Development of the Cirripedia. 
By Dr. Aveust Kroun*. 
[With a Plate.] 
Tue results which we have lately obtained—thanks to the labours 
of Burmeister+, Spence Bate{, and Darwin §—upon the develop- 
ment of the Cirripedia are so satisfactory, that we might already 
congratulate ourselves upon an insight into the manifold changes 
passed through by the young animal from its birth to the attain- 
ment of its perfect form, if there were not a sensible gap still 
vacant. It is still unknown by what intermediate steps the 
larva, which, during the first period of its development, agrees 
in so many respects with the young forms of the Entomostraca, 
especially the Copepoda, passes to the subsequent Cypris-like 
form. During my residence in Funchal, and afterwards at 
Messina, I was able to obtain some information upon this still 
-unexplained point. Before communicating my observations on 
this subject, [think it will be necessary in the first place to describe 
the form presented by the larva during the first period of its 
development, and then to refer more particularly to individual 
organs which are peculiar to it in its later Cypris-form. 
At a certain stage of development, when the larva has moulted 
two or three times after its escape from the egg, we distinguish 
in it a broad body (Vorderleib), frequently truncated in front, and 
diminishing posteriorly, followed by two slender processes extend- 
ing backwards (Pl. VII. fig. 1). The superior process has the 
form of a straight, extended, and often very long spine; the in- 
ferior one, which is stouter, runs, gradually tapering, to a forked 
extremity, and is, especially in the later stages, capable of being 
bent and extended. I characterize it provisionally as the caudiform 
appendage ||. The body is covered on the dorsal surface with a 
carapace or shield, the anterior angles of which are produced 
into two thin horns, furnished with a few curved bristles at the 
apex §. On the lower surface the body is provided with three 
pairs of swimming feet, and with a proboscidiform process spring- 
ing freely from the middle between the last pair. Close behind 
the anterior margin of the carapace, a small eye, provided with 
- * Translated from Wiegmann’s Archiv, 1860, p. 1, by W. S. Dallas, 
F.L.S. 
+ Beitrage zur Naturgeschichte der Rankenfiisser, 1843. 
t On the Development of the Cirripedia, Annals, ser. 2. vol. viil. p. 324, 
1851. 
§ Monograph of the subclass Cirripedia, 1851 & 1854. 
|| From the figures to Spence Bate’s memoir, I cannot but think that 
this observer regards the spmous process as a prolongation of the carapace 
next to be mentioned, which is certainly wrong. 
§ Burmeister and Darwin regard these horns as antennz, but erro- 
neously, as will hereafter appear. ; 
