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DE. E. YON WILLEMQES-SUHM ON THE 
the daytime these larvae were scarcer (many of them came up, however, from a depth 
of 60 fathoms), but at night they were so common that large bottles could be filled 
with them. The question (which had been left open by Dohrn) to which Cirriped these 
extraordinary Nauplii might belong, presented itself of course again to us, and we tried 
to obtain all the Lepadidae we could. In a day or two we got into large streams of 
floating Lepads ; and now it was an easy thing to get as many as we liked, and to bring 
up in our globes such stages of the large Nauplii as had also been taken by us on the 
surface, and which clearly belonged to them. Then, again, when catching large quan- 
tities of larvae, we got among them (especially when the net was skimming the very 
surface of the water), (1) some which were ready for the metamorphosis into the Cypris 
stage, (2) the Cypris itself swimming and creeping about or just settled on a dead 
Velella, and (3) the stage in which the Cypris ? shell is about to be thrown off, in order 
to make room for the growing valves of the young Lepas. 
The species to which this barnacle belongs is decidedly the very variable Lepas 
fascicularis as described by Darwin, l. c. p. 92. The formation of the balls, the brittle- 
ness of the shell, and the peculiar shape of the valves show this at once ; there are, 
however, some differences which must be mentioned in detail, as possibly this North- 
Pacific species deviates from the Atlantic one not only by these small differences, but 
also by possessing another nauplial form, in which case it would be decidedly necessary 
to separate this Pacific form from it. In most specimens which I dissected I found six 
teeth in the mandible, not five, as is the ordinary number. Sometimes, however, there 
are five on one side and six on the other, as in the case which I have figured (Plate 15. 
fig. 30, a and b), showing that this difference has no constant value. The maxillae have 
sometimes four steps (the regular number as given by Darwin) ; but they have more 
commonly only three steps besides the two large, unequal, upper spines (fig. 29). 
These are the only differences from an ordinary Lepas fascicularis which I can find ; 
and they merely show that this Pacific - form is a variety of the Atlantic one, in case 
there should not be a difference in the development of the two. As we know, how- 
ever, nothing about the five stages through which the Atlantic form has to pass if it 
follows the same mode of development as this one, and as no “ Archizoea” has as yet 
been described from the Atlantic, this question must remain an open one until further 
information. 
I will now proceed to give an account of the development of Lepas fascicularis, men- 
tioning the publications which refer to certain phases, in their respective paragraphs. 
I. Development of the JEgg and of the youngest Nauplius. 
The ovarium, a cellular body at the top of the pedunculus, has a light bluish colour, 
as in all Lepadidae. It consists of tubes and their caeca, in which we find the ova in a 
more or less advanced state of development. In a young specimen one finds the ova 
sometimes in different stages, but in the older ones nearly all the ova in the ovary (with 
the exception of those “ mother cells ” which do not develop) are in the same stage of 
