40 E. RAY LANKESTER. 
the other hand, of these bodies, they being reciprocally 
vicarious within small limits. But the feature in which 
they differ from the nuclei of cleavage segments is this, that 
no area becomes segmented around them. They make their 
appearance in great numbers near to but not at the surface 
of the egg-mass, extending first in ring-like series in advance 
of the margin of the klastoplasts, but subsequently appearing 
indiscriminately over all parts of the egg. The klastoplasts 
as they advance to the parts where these bodies already he 
grow over them, occupying a higher stratum of the egg. 
These nucleus-like bodies can be observed in all their stages 
of development in living eggs, and I have satisfied myself 
that they commence as minute points, gradually increasing 
in size like other free-formed nuclei. I distinguish them as 
“autoplasts.” ‘They form a very large part of the blastoderm, 
but the whole of its superficial layer (epiblast) is formed by 
cells which can be directly traced by successive fissions to 
the first cleavage segments of the patch of formative mate- 
rial segregated to the cleavage-pole of tie egg, in fact are 
klastoplasts. 
The autoplasts (a) are seen in fig. 1, where the overlying 
klastoplasts are omitted. 
The autoplasts continue to develop near the surface of the 
yelk in Loligo until a very late stage of development. In 
fact, they are present in the contents of the reduced remnant 
of the yelk-sac possessed by the young Loligo at birth. 
Comparatively little importance would attach to the 
autoplasts if we did not know their subsequent development. 
They become branching, stellate, and fusiform cells, under- 
lying the klastoplasts, and form that contractile tissue which 
gives to the yelk-sac its power of rhythmical contraction 
(similar to the embryonic contractile sac of Limawx, &c.), the 
observation of which I have previously recorded. ‘They also 
form a large portion of the deeper substance of the embryo 
itself. In fig. 1, x, the klastoplasts from near the upper pole 
of the egg are represented. In A we have a group of auto- 
plasts, of which ef and cd are seen to possess filamentous pro- 
longations. They are seen through the living transparent 
klastoplasts. Acetic acid gives the result seen in A’. The 
klastoplasts s s come to view as a continuous pavement, whilst 
the autoplasts shrink and granulate and show nucleus and 
nucleolus. When the autoplasts first appear, they, like the 
nuclei of cleavage segments, are not affected by dilute acids. 
The autoplasts of Loligo, of which I have just been 
speaking, are represented by similar bodies in Sepia. In 
Octopus the autoplasts are present but differ, since they are 
more irregularly disposed, often of large size, and present 
