148 ARTHUR WILLEY. 
swam about on the top all the time. About an hour after- 
wards I took the latter out in a canoe to observe its move- 
ments in one to three fathoms of water. On placing it in the 
sea it remained at first on the surface, swimming actively 
backwards, i.e. with the shell directed forwards. It fre- 
quently swam to the bottom and back again to the surface— 
often also swimming in the middle stratum of water. I have 
never found any necessity for framing an elaborate theory as 
to the rising and sinking of the shell. 
3. The Position of the Spadix or Hectocotylus.— 
I was surprised to find that the spadix in the male developed 
variably on the right and left sides of the cephalic system. 
Out of thirty-seven males which were examined ad hoe, 
twenty-three had the spadix on the left side, and fourteen had 
it on the right side. 
4. Pallial Arteries.—I will say a few words about the 
pallial arteries, in order to refer to the arterial blood-supply of 
the siphuncular pedicle. Anatomical evidence seems to point 
to the conclusion that the latter structure has more of a 
vestigial than of an actively functional physiological import- 
ance. mbryology will show whether or not it has any original 
relation to the primitive shell-gland. 
The so-called lesser aorta of Owen, arising from the anterior 
slightly incurved margin of the heart, divides immediately, as is 
known, into two branches. These are respectively the anterior 
and posterior pallial arteries. 
The anterior pallial artery bends inwards and somewhat 
downwards to the middle line, and then runs forwards below 
the skin on the surface of the renal sacs. At the point where 
it turns forwards a small intestinal branch is given off. Arrived 
at the anterior limit of the renal sacs, the anterior pallial 
artery passes into the substance of the mantle, and runs 
towards the free margin of the mantle, shortly before reaching 
which it bifurcates into two main marginal arteries, from which 
numerous radial arteries are given off (see Fig. 1). 
Exactly at the point where the anterior pallial artery passes 
into the substance of the mantle a pair of branches, right and 
