[137] CEPHALOPODS OF NORTHEASTERN COAST OF AMERICA. 
canary-yellow ones. On the lower side they are so thinly scattered 
that they leave much of the translucent bluish white ground-color visi- 
ble between them; along the median ventral line the spots are more 
numerous, producing a distinct median stripe. The caudal fin is clear 
bluish white beneath, and very translucent, becoming almost transparent 
near the margin. 
Exposed part of the siphon similar to the ventral surface of the body, 
but with the spots more sparse, and mostly disappearing near the margin 
and at the base; lower side of the head, in front of the eyes, sparsely 
spotted. Outer and upper sides of the upper arms and outer surfaces 
of the ventral pair similarly, but somewhat more densely, specked ; both 
sides of the ventral arms and lower sides of the lateral arms pinkish 
white and unspotted. Tentacular arms pale translucent, bluish white, 
with the outer surface, except at base, rather thinly specked with small 
purplish chromatophores; the inner surface and upper side of the tip 
and the suckers are translucent white; rings of suckers white. 
On the inner surface of the dorsal and lateral arms, between the 
suckers, there are a few large chromatophores, and a double row of them 
runs out obliquely on the muscular thickenings of the marginal mem- 
brane, alternating with the suckers, on each side; suckers pure trans- 
lucent, bluish white (becoming yellow or brown in alcohol). 
The pupils of the eyes are deep bluish black; on the upper side they 
are encroached upon by a sinuous downward extension of the iris, 
which is silvery or pearly white, with brilliant, green, opalescent reflec- 
tions at the upper margin. ; 
‘ Sexual differences. 
The sexes differ to a considerable extent in proportions. If we com- 
pare specimens of equal length, the female will have the body relatively 
stouter and less tapered posteriorly than the male; the head is decidedly 
larger;* the arms are longer; the suckers are usually distinctly larger, 
especially those of the tentacular arms. But if we compare specimens 
having the head and arms of equal size, the male will be found to have 
a decidedly longer, more slender, and more tapered body, and a some- 
what longer and narrower fin. (See Table B, for comparative propor- 
tions.) 
In the adult male the circumference of the head to the mantle-length 
usually varies from 1:2.55 to 3.45, averaging about 1:3.10; in the female 
from 1:1.75 to 1: 2.45, averaging about 1:2.25. 
The ratio of the breadth of the fin to the mantle-length, in the male, 
varies from 1:2.12 to 1:2.45, averaging about 1:2.25; in the female, from 
1:1.70 to 1:2.12, averaging about 1:1.90. 
*Some of the nominal European species of Loligo, that have been based on the 
smaller size of the head, arms, and suckers, are probably only the males of the common 
species. The sexual variations in this genus have apparently been very imperfectly 
understood by European writers generally. 
