DEVELOPMENT OF THE CEPHALOPODA. 39 
areolated pellicle (ce) which the egg brought with it from the 
ege-capsule. When the egg arrives in the oviduct the 
germinal vesicle has disappeared ; ; 1t is still present in full- 
sized ovarian eggs. ‘The egg is now a homogeneous mass of 
granular elements with a small amount of intergranular 
plasma. The granules are modified cells of the inner egg- 
capsule; the plasma chiefly: formative material. The 
further process of development begins with a segregation of 
formative matter and the breaking » up or segmentation of this 
segregated matter—involving to a certain extent the un- 
segr egated major portion of the egg. A small cap of forma- 
tive matter segregates to the narrower pole of the egg. It 
presents no nucleus, persistently, though a nucleus may 
appear in it at the first. The cleavage has been described 
by Kolliker ; it does not proceed so regularly as he has re- 
presented. A nucleus is to be seen in each of the first 
cleavage segments, but in the later segments there is great 
irregularity i in this matter. I have most fully satisfied my- 
self that temporarily many of the segmentation products are 
devoid of nucleus. 
Passing over the details of this process, which I reserve for 
another occasion, I proceed to the period when the “ cleavage ” 
may be said to have ceased. A cap of cells at one pole of the 
egg is the result of the cleavage of the mass segregated at this 
point (see fig. 1*). I call these cells “ klastoplasts.” They are 
not sharply cut off from the rest of the egg, nor is the segre- 
gated mass from the cleavage of which they arise, but “the 
eroup of klastoplasts thin out at the periphery as it does, and 
become fused with the undifferentiated yelk. They extend 
their area at first by growth along lines corresponding to the 
chief radial grooves of the cleavage, a marginal cell of the 
cap of klastoplasts at such a point growing by accretion of 
formative material (continued segregation) and then breaking 
into two. When the cap of klastoplasts has spread one third 
over the egg, its marginal cells grow by a regular increase in 
size and consequent fission, taking place equally all round 
the margin. But before the superficial extension of the cap 
of klastoplasts has commenced there appear in a deeper 
stratum of yelk pellucid nuclei, at first arranged in a circle 
around the cap of klastoplasts, as I have figured them in 
‘Annals and Mag. Nat. Hist., April, 1873. ‘These pellucid 
nuclei are of the same nature as the nuclei of cleavage sec- 
ments. ‘They might be taken for them, and no doubt the 
first series of them are physiologically convertible with such 
nuclei. I believe in the eggs of Loliyo there may be according 
to season an increase of nucleated cleavage segments, or, on 
