two new Species of Hectocotyle. 11 
suckers, which are disposed alternately, and bear the strongest resemblance to 
those of the Tremoctopus itself. 
The posterior part of the body is a large oval sac, of 5 lines in length, to 
which the penis is appended. The sac is quite as large as the largest part of 
the body, and incloses a great many convolutions of a small canal and one 
large duct. The penis is situated on the abdominal surface, and takes its 
origin from the foremost part of the oval sac: it is conical and partly free, 
partly confined in a delicate membranous sheath, which is attached to the 
ventral aspect between the last six suckers; its form and length vary accord- 
ing as it is contracted or extended ; in the first case it is 4 lines long, $ a line 
thick, and curved; in the latter, 7 lines long, } of a line thick, and nearly 
straight. 
2. Structure. 
a. Skin. 
The skin of the animal consists of two layers; the exterior is the epidermis, 
formed by delicate, polygonal cells, of a diameter of 0:018-0:036", which 
contain round nuclei; the interior, the corium composed of cellular tissue, 
the outer fibres of which are disposed longitudinally, and the inner trans- 
versely. The coloured spots, already mentioned, form a very remarkable 
object in the description of the skin; each of them is a cell, containing a 
nucleus and a great many coloured granules, and exhibits during life the 
same curious phaenomenon which R. Wagner has discovered in the pigment- 
cells of Cephalopoda, viz. a regularly alternate expansion and contraction. As 
in the example just quoted, the colour of the cells varies according as the 
granules are assembled together in a mass or scattered about in the expanded 
cell. With regard to the power which effects these contractions, it is not yet 
proved whether it lies in the contractile membrane of the cells, as Wagner 
supposes, or in the contractile cellular tissue which surrounds them, an opi- 
nion which I have lately advocated. 
I have yet to mention some peculiar minute pores which are found on the 
anterior part of the ventral surface. They are arranged in rows of four or 
five on each side between the mesial line and the suckers, thus forming a 
continuous series. Each opening is elliptical in figure, the longest diameter 
being 0:024—0:012 P. L., and conducts to a canal of the same size, which 
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