262 Description of a Species of Caligus. 
with an internal granulose structure. The duct, which is at- 
tached on the outer margin, isa slender vessel, of a thin membra- 
nous nature. It continues of a uniform size through the thorax 
to the central parts of the abdomen, where it gradually enlarges 
and undergoes a few convolutions. 
A short distance below the convoluted portion, there is a small 
oval gland, with well-defined limits, contained within a distinct 
sac. It is apparently composed of several concentric parts, of 
which three are very apparent; there are two less distinct. Its 
interior is a transparent globule; the outer coats are less trans- 
parent, and the one adjacent to the interior, the least so. The 
central part of this gland is connected with a small sub-corneous 
tube, which gradually enlarges, and passes into the anterior ex- 
tremity of the above convolutions. On one occasion, when we 
had separated this gland and its duct from the abdomen, a fluid, 
containing particles similar in appearance to those in the blood, 
rapidly poured out. The convoluted vessel appears therefore to 
receive the secretions of two seminal glands, and probably corres- 
ponds to the vas deferens. Though much time has been enl- 
ployed in searching for the exit of the vas deferens, we are yet 
uncertain on this point. It is presumed, from the appearance of 
the parts, that it terminates either on the outer surface of the lap- 
pet at the extremity of the abdomen, or beneath this organ. 
The ovaries in the female have the same situation and attach- 
ments as the spermatic gland in the male. (Pl. V, fig. 18.) They 
are however much larger, and extend above the stomach nearly to 
its centre. They may be distinctly seen through the back shell. 
They appear to contain a long convoluted vessel, which gradually 
diminishes in size, from its anterior to its posterior extremity ; but 
whether this be truly its nature, cannot be determined. The duct 
arising from its margin, extends without any variation in its size, 
till it reaches the posterior joint of the thorax, where it enlarges 
gradually, and continues to increase as it enters the abdomen. In 
the gravid female, it passes through the abdomen, with a few 
convolutions, and extends out at the vulva, in the form of a long, 
whitish, nearly cylindrical membranous tube. This external por- 
tion of the oviduct is often a little longer than the animal. 
The vessel in the ovary does not appear to contain divisions in- 
dicating the presence of eggs; cane the oviduct usually contains 
eggs through its whole extent. Where exserted, it is very dis- 
