DEVELOPMENT OE CIKRIPEDIA. 
137 
preceding ones. There is accordingly no doubt about their being stages of the 
development of one and the same animal. This, besides, is shown clearly enough by 
the similarity in the tail, its spine, and the labrum of the two forms, which have been 
figured on Plate 11. 
Before I give, however, the description of the stages through which the Cirriped has 
now to pass, I must explain the name Arcliizoea. It has been given by Dohrn to a 
Nauplius which has a length of 4-5 millims., a height of 1^—2 millims., and has the 
shape of a Chinaman’s hat. It has a large caudal spine and a dorsal one, six movable 
spines on the tail, besides many fixed ones, a large labrum, and a very spiny caparace. 
These Nauplii have been caught off the coasts of Chili, and been described by Dohrn in 
a most perfect way. Why, however, he gave to it a generic and a specific name, though 
he clearly knew that it was a Cirriped Nauplius, I do not know ; for he could have 
published his ideas about the “ complete Zoea, which as a perfect larval form has 
vanished from the development of Cirripeds,” and the remains of which may be found 
in the dorsal spine and perhaps in some movable spines on the tail, without doing so. 
I have also caught the larvae which he has called Arcliizoea gig as, and may at once 
add that I have good reasons to believe them to be the Nauplii of Lepas australis. 
Thus I was able to study these two different forms alive, and have come to the conclu- 
sion that they are true Nauplii, and have nothing whatever to do with a Zoea. 
“ Arcliizoea gig as ” has a length of 4-5 millims., and is chiefly distinguished from our 
Nauplius by the shortness of its spines, the multitude of gland- openings in processes 
(spines) all over the carapace, and by the number of spines on the labrum (five on each 
side, hi our case two). I got some specimens from the surface off the southern coast 
of Australia, which I believe to belong to Lepas australis for the following reasons : — 
Lepas fascicularis, to which undoubtedly our Arcliizoea belongs, is (to use Darwin’s 
words) “ certainly much the most distinct of any in the genus ; and Mr. Gray has 
proposed to separate it under the name of Dosima; but considering the close simi- 
larity of the whole organization of the internal parts, together with the transitional 
characters afforded by L. australis , I think the grounds for this separation are not 
quite sufficient.” And in describing Lepas australis he says, “ this species has some 
affinity to L. pectinata, but it is much more closely related to L. fascicularis . I 
believe this species is confined to the Southern Ocean, and perhaps there represents 
L. fascicularis of the northern seas.” Now larvae which are very nearly allied to those 
L. fascicularis have been found in the Southern Ocean ; and it seems to be almost 
certain, after what has been said about the relations of L. australis to L. fascicularis , 
that the Nauplii hi question belong to the former species. This is all the more pro- 
bable as the pupa stage of Lepas australis, which has been described by Darwin as 
having a length of 2-3 millims. (0-067-0T of an inch), corresponds in size to the large 
Nauplii described by Dohrn, and resembles very closely in all points of its organization 
the pupa of Lepas fascicularis, which I am going to describe below. W e ourselves 
caught these large Cyprides of Lepas australis and the young barnacles of the 
