REPORT ON THE CIRRIPEDIA. 
39 
think they can safely he described as bipolar, for their body can be followed up as a very 
pale process in the direction of the supracesophageal ganglion as well as in the direction of 
the eye. In both directions these processes are placed, like the ganglionic cell itself, quite 
in the interior of the nerve. Close to the eye the nerve shows a second swelling which 
contains also a distinct ganglionic cell, and it is by this swelling that the nerve is laterally 
attached to the eye. Each of the two other slightly thinner nerves, which run between 
the two stronger ones, has also a swelling at about the same distance from the eye. The 
two nerves unite together where this swelling is thickest and where each contains a 
ganglionic cell ; they then part again and separately run towards the eye, which they 
reach at its frontal extremity, i.e., that extremity which is directed towards the supra - 
oesophageal ganglion. I have not been able to study the way in which the nerves enter 
or are attached to the pigment spot. Bound about the spot a network of fibres of greater 
or less capacity can easily be made out ; yet it is extremely difficult, not to say impos- 
sible, to ascertain with certainty the nature of these fibres. Some of them are no doubt 
nerve-fibres, while others belong doubtless to the connective tissue. 
The way in which the ganglionic cells are placed in the interior of the nerves slightly 
resembles what Leydig observed in the case of the sympathetic nerve-fibres of insects. 
He observed 1 (in Bombus terrestris) in single fibres of the so-called sympathetic nerves, 
a nucleus here and there with a granular mass surrounding it, forming a kind of bipolar 
ganglionic cell “ in der Anlage.” 
Neither in Lepas anatifera nor in Lepas fascicularis could I distinguish the two 
little lenses which Darwin says he has observed. Nor do I think that this is owing 
to any fault in my observation. Darwin may have observed living, or at least fresh, 
animals, and the lenses may have disappeared under the influence of the alcohol. But I 
think it is more probable that Darwin, who used only a feeble magnifying power, has 
mistaken the ganglionic cells for lenses. What he calls the two small perfectly distinct 
oval ganglia, are probably the swellings of the optic nerves which in Lepas anatifera 
contain two distinct ganglionic cells. 
As regards the sessile Cirripedia, and especially different species of Balanus, the 
experiments of different naturalists have shown that they are sensible to a difference 
between light and shadow. I do not know whether similar experiments have ever been 
made on pedunculated Cirripedia. Should they give the same result, and I think they very 
probably would, even then I should hesitate to consider the rudimentary simple eye placed 
on the external suiface of the stomach as the organ of this function. 
1 Leydig, F., Bau des thierischen Korpers, Tubingen, 1864, p. 205. 
