on the Principle of Cephalizdiion, . 31 
ates with the axis vertical, the —4 r pole being below, and — 
the Monomyarian horizo zontal again. It must be remembered 
that the above considerations are pci in their most general 
sense, representing only the mean for each group, many of them 
erhaps erroneous. They are given rather for the purpose of 
indicating a further path of inquiry, which the writer considers 
fruitful and intends to follow, than as woe in any way settled. 
In ascertaining the mean position of the antero-posterior axis 
for the whole branch of Saceata, (that is, the average) we find 
that a line at an angle of 45° would represent its position in 
nature; the lower end being anterior. In the Radiates a line 
through the mouth to the opposite region of the body would 
stand ee In Articulates the antero-posterior axis would 
be horizontal. Among the Vertebrates, Fishes would be hori- 
gotta, = in Articulates ; Se ora have the head slightly ele- 
vated; Birds and Mamm mals still more elevated; so that a mean 
line, for ests classes might be drawn at an angle of 45°, the 
cephalic region being uppermost. Man stands vertical. Thus 
in a diagram we would have the following: 
2. 
he 
Pe Ree eee 
mise Articulata.* 
Saccata. 
. Radiata. 
nowhere does this character predominate so universally, nor is 
it expressed so simply as in the Mollusea; the leading idea as it 
were. It was shown also that, essentially, the heart is on the 
euter bend of the intestine, or Lae that and the sac wall, 
while the principal nerve mass was on the inner bend of the in- i a 
testine. We would thus state tes characters. - 
SACCATA, 
(1.) Animals of varied forms, without a radiate structure and a 
without articulations 
2.) Stomach and viscera enclosed aap Lae which. may 
closed or open, at either one or both 
