320 
A. E. Yerrill — North American Cephalopoda. 
11th of June, in the vicinity of New Haven, many of these eggs con- 
tain embryos in advanced stages of development (Plate XLI, tigs. 2, 
3 ; Plate XLY, fig. 4). The embryos, before hatching, can swim 
around inside the eggs. 
These embryos are very beautiful objects to observe under the 
microscope. 
Even at this early period some of the chromatophores are already 
developed in the mantle and arms, and during life, if examined under 
the microscope, these orange and purple vesicles can be seen to con- 
tract and expand rapidly and change colors, as in the adult, but the 
phenomena can be far more clearly seen in these embryos owing to 
the greater transparency of the skin. In the young the chromato- 
phores are very regularly and symmetrically arranged, on the arms, 
head, and mantle. At this stage of development the eyes are brown. 
In these embryos a remnant of the yolk-sac (y), appears to protrude 
from the mouth, but it is really connected with the space around 
the mouth and pharynx, and into this it is eventually absorbed. 
The more advanced of the embryos were capable of swimming 
about, when removed from the eggs, by means of the jets of water 
from the siphon («), which is developed at an earlier stage. The 
arms ( a"-a "") are then short, blunt, very unequal, with few minute 
suckers ; the dorsal arms are very small, while those of the 2d and 
3d pairs are successively longer, and have distinct suckers; the ten- 
tacular arms (a'") are longer and larger than any of the others, and 
have larger suckers, which already, in some examples, can be seen to 
form four rows; the ventral arms (a"'\) are about ns long as the 2d 
pair, and bear sevex*al suckers. The mantle (m) is short, and the 
caudal fins (f) are very small, short, lateral, and separately attached 
to each side of the blunt posterior end of the body, thus recalling 
their adult condition in JRossia. The eyes ( e ) are large and promi- 
nent ; the rudimentary beak (d) and odontophore (Z) are distinctly 
visible. The two otoliths (o) are very distinctly visible, as highly 
refracting ovate bodies, above the basal part of the siphon, one on 
each side. The ink-sac («), attached to the rectum (£), is conspicuous 
on account of its dark color; the gills (y) are provided with a small 
number of transverse processes; the heart (h) and the branchial 
auricles ( h ' h') are easily seen, while they continue to pulsate. The 
pen exists only in a rudimentary condition, as a thin cartilage. 
During July and August the young (fig. 5) from less than a 
quarter of an inch to an inch or more in length, swim free at the 
surface, and may often be taken in immense quantities with towing 
