252 OIRCULATION IN GASTEROPODA AND CEPHALOPODA. 
is distributed to the gills e; and thence it returns to the heart, 
after having undergone aeration. Now if a second heart had 
been placed on the trunk / f, just as it is about to subdivide 
for the distribution of the blood to the gills, the circulation 
would have been analogous to that of Birds and Mammals. 
There is a great variety in the position of the gills in Mollus- 
cous animals, and a corresponding variety in the situation of 
the heart, which is usually placed near them. In the Doris 
the gills are arranged in a circular manner, round the termina 
tion of the intestinal canal ; but in many Mollusca they form 
straight rows of fringes on the two sides of the body. In 
these last, the heart not unfrequently has two auricles ; but 
these are not analogous to the two auricles of Reptiles ; for 
each has the same function with the other—the reception of 
the blood from the gills of its own side. 
291. There is a very interesting variety in the conformation 
of the heart in the CepHaLopopa, or Cutile-fish tribe ; which 
vb cs ve as b 
H Wat Dats f' 
D ! ‘ | “S| E 
7A A=: 
p— AS Loh) d 
a -ille fe 
SS, N j AS ab 
bi! £F ZS 
Fg ZS 
— AN 7 YP ge =e, 
aaa, \) Oa - 
——, e ome 
--- op 
ls ) 
i) 
Fig. 140.—Cincunatine APPARATUS OF CUTTLE-FISH. 
seems to form a connecting link between the plan of the cir- 
culation that prevails among the Mollusca in general, and that 
