JOURNAL OF MICROSCOPICAL SCIENCE. 
KXPLANATION OF PLATES IV and V, 
Illustrating Mr. Ray Lankester’s Observations on the 
Development of the Cephalopoda. 
N.B.—The figures are zot drawn to one scale. 
Fic. 1.—Hgg of Loligo represented without its coverings; the blasto- 
derm has spread over four fifths of the egg’s surface. The autoplasts (a) 
are seen through the transparent klastoplasts, which only appear in optical 
section as the layer s. 
Fie. 1 4.—Six autoplasts from the yelk-sac-pole of a Loligo’s egg, in 
which the blastoderm has nearly involved the whole surface. The same 
autoplasts are seen in Fig. 1 a’ after the addition of dilute acetic acid. 
This has brought into view the superficial and large klastoplasts, s s, and 
has granulated and contracted the subjacent autoplasts. 
Fie. 1 x.—Klastoplasts from the surface of the specimen drawn in 
fig. 1. 
"Fre. 1*.—Vertical section through the cleavage area of a Loligo’s egg, 
hardened in osmic acid. The annular peripheral thickening of the mass of 
cleavage-cells is seen in section: also observe the thinning out of the 
cleavage patch at its extreme periphery. es. The horny egg-shell. 
cp. Cleavage products. y. Yelk. 
Fic. 1* *.—Portion of a section of an egg of the same stage as that 
seen in Fig. 1 hardened in osmic acid. The long axis of the egg runs 
right and left in this section, the cleavage pole being towards the left. A 
portion of the blastoderm is seen in section, and a large mass of yelk; es, as 
before, is the egg-shell. Below we have & the klastoplasts and a deeply 
stained layer ; below that a, which appears to consist of autoplasts. The 
light spaces in the yelk may represent merely vacuoles, but are more 
probably the points occupied by gradually differentiating autoplasts. 
Fic. 2.—Kgg of Octopus in its horny shell (es), which has a stalk (ses) 
four times the length of the egg-shell itself. The shaded part (4) indicates 
the gradually extending cap of klastoplasts ; aa are autoplasts. ce. The em- 
bossed “ capsular envelope” of the egg—a delicate pellicle which the egg 
derives from the inner stratum of the ovarian capsule—and which in Octopus, 
as also in Loligo, may be seen thrown off in delicate shreds when the first 
ciliary movements commence. 
N.B.—In Octopus, as soon as the blastoderm is complete, the egg 
reverses tts position in the egg-shell, the cleavage pole taking up its position 
nearest the egg-stalk, whilst the yelk-sac-pole occupies the opposite end 
of the chamber. ‘This total reversal of position also takes place in 
Argonauta. 
Fie. 2 a—4. Deep-lying autoplasts from the egg of Octopus, showing 
radiating lines of granules as in the formation of nuclei described by 
Oellacher and by Fleming. 3B. A pellucid autoplast ; 3’ its appearance 
after dilute acetic acid. X. Klastoplasts from the cap k of fig. 2. 
Fic. 3.—Part of a vertical antero-posterior section of a Loligo embryo 
hardened in picric acid and absolute alcohol (Kleinenberg’s method). 
ep. Epiblast. mes. Mesoblast. ym. Deepest layer of embryonic cells covering 
in the yelk, and hence to be called yel& epithelium. al. Lumen of alimen- 
tary feral (aboral portion). ps. Pensac, still open. mff. Edge of the 
mantle. 
Fic. 4.—. “similar section of an older embryo. y. Yelk. az. Anal 
depression «” 4e epiblast. Other letters as in fig. 3. 
Fie. 5.—a similar section of a yet older embryo. pv. Primitive 
vascular spaces in the mesoblast. zs. The rudiment of the ink-sac 
