1877.] Barnacles. 105 
(A, 1). The circulatory system is very imperfect. There is a 
dorsal vessel (A, d) which I have succeeded in injecting; the 
blood flows between the muscles in broad currents and is not 
confined in closed vessels, Respiration is probably performed 
by the whole surface of the body. The barnacles are generally 
hermaphroditic. The testes (A, ¢) are found surrounding the 
alimentary canal and extending into the filiamentary append- 
ages and the bases of the cirri; they consist of branching tubes 
connecting with lobular ceca. The Vasa deferentia (A, v) are 
disposed one upon each side. They follow an undulating course 
and unite at the base of the penis (p) and proceed as a single 
tube to the end. The ovaries are found in the peduncle (A, 0) 
and present the same general appearance as do the testes. 
The nervous system is easily dissected by laying the specimen 
upon the dorsal surface (after removing all the valves) and cut- 
ting away in front of the esophagus. This will expose the 
supra-esophageal ganglia (C, s), which will be readily recog- 
nized, as they present the same shiny white appearance that al- 
ways characterizes nerves. From the commissure connecting 
these ganglia a single nerve arises and proceeds forward in the 
median line. The optic nerves originate on each side, have each 
an enlargement, the ophthalmic ganglion (C, 0) and unite in the 
rudimentary eye (C, e), which is imbedded in the membranes of 
the body. Exterior to these arise the nerves which supply the 
peduncle. From the posterior angles of the supra-cesophageal 
ganglia a nerve on each side (0, œ) passes backward around 
the cesophagus and unite in the infra-osophageal ganglion 
(C, n). From the anterior portion of this arise the nerves 
which go to the adductor-scutorum (C, a) muscle; on the sides 
the nerves which go to the first pair of cirri have their origin ; 
from the dorsal surface (the under surface as the specimen lies) 
are given off two nerves which are distributed among the 
viscera. The second, third, fourth, and fifth thoracic ganglia 
follow each other, are connected by commissures, and give rise 
to nerves supplying their respective cirri. The sixth ganglion is 
most invariably united to the fifth, and from it arise the nerves 
going to the sixth pair of cirri and the penis. In one specimen, 
however, I have found the fifth and sixth ganglia connected by 
distinct commissures. 
In the sessile Cirripedes the internal anatomy does not differ 
greatly from the form above described. They are best dissected 
by removing the animal through the base (the portion by which 
