DEVELOPMENT OE CIEEIPEDIA. 
149 
is formed. The cirri have acquired a greater number of segments (fig. 26) ; and the 
young Lepas, which has now a length of 4 millims., is complete. 
Conclusion. 
The chief object of this paper has been to give a complete history of a Lepas 
development which hitherto had never been worked out. The first and the last 
stages were known in some species, and in another species the intermediate pelagic 
stages had been described by Dohrn ; but it was not even known to what family of 
Cirripedia these Nauplii belonged. This is quite natural, as all the work for such a 
complete development must be done under conditions which scarcely ever had been 
realized before this ship left the shores of England. 
There are. only few points in this paper which will enlarge our ideas about the 
morphological relations of Cirripedia very much, in so far as each of the larval stages 
were known to exist before ; but it settles the question to which of the Cirripedia the 
large pelagic Nauplii belong, and it gives further details about their intimate structure. 
It also gives certain indications which allow us to say, almost to a certainty, to which 
of the Le^as species the larvae belong which Dohrn got in the south, and which have 
been taken by ourselves to the south of Australia; but it likewise gives evidence that 
there are no traces of a Zoea stage in the course of the Lepas development. The Nauplii 
are very highly organized, but there are no essential differences between them and the 
other embryonic forms which we have been accustomed to call Nauplii. The name of 
Archizoea might, I think, be left to keep up the remembrance of Dohrn’s discovery of 
the interesting Lepas larvae ; but speaking of the Lepadidae in general, I think it would 
only confuse matters if it were said that they pass through an Archizoea stage. This 
would imply that the later Nauplius stages of Lepas have a different morphological 
value from those of Balanus or other genera, which I think they have not. 
Description of the Plates. 
PLATE 10. 
Eig. 1. Development of the ovarium ( m ) : n, the ovum nearly filled with yelk, still 
showing the germinal spot. 
Fig. 2. Ovarian tube with young ova in the beginning of their development. 
Eig. 3. Ovarian tube with nearly mature ova. Among them some undeveloped cells 
(oi), perhaps the mother cells of the ova. 
Fig. 4. Complete ovum, before the beginning of the segmentation, taken from the 
ovisac. The germinal vesicle is not visible. Nat. size, 0‘26 millim. 
Figs. 5 & 6. First stages of segmentation. Four blastodermic cells have formed 
themselves. 
Fig. 7. Segmentation of the yelk goes on, but is not clearly visible. More blastodermic 
x 2 
