DEVELOPMENT OF BOLOCERA 519 
outer zone. Just under the egg-membrane is a thin layer 
where the first-named granules are very numerous, the clear 
spherules absent, and the yolk-spheres few in number. 
Bolocera has the largest eggs of all the Clyde Anemones 
I have investigated. Their diameter, 1-1 mm., compares with 
0-1 mm. for Metridium dianthus, 0:3 mm. for Anthea 
cereus, 0-1 mm. for Sagartia, 025mm. for Adamsia 
palliata, 0mm. for Urticina coriacea (the shore 
Urticina), 0-7 mm. for Urticina crassicornis (the sub- 
merged Urticina). Full-grown ovarian eggs of Gonactinia 
prolifera and of Actinia equina measure respectively 
0-07 and 0-15 mm. in diameter. The Bolocera egg-membrane 
and its spines resemble but are hardly so strong as those of 
Urticina. The egg-contents of the two are much the same. 
Anthea (and Actinia equina, according to Lacaze Duthiers) 
has spiny egg-membranes, but in Metridium, Sagartia, and 
Adamsia the membranes in question are smooth. 
In Bolocera, as in Urticina (Appelldf, 1), the fertilized 
nucleus gives rise to a number of daughter nuclei (sixteen in 
Urticina) before the egg-mass undergoes cleavage. In particular 
cases I have estimated the number as not less than twenty- 
four. The fertilized nucleus probably lay at a point some- 
where in the deeper layer of the outer zone, about a third 
of the diameter of the egg inwards from the surface. The 
daughter nuclei, as they increase in number, spread laterally 
at this level from the point in question until they are more or 
less equally distributed all round. In the egg illustrated by 
fig. 1, eight nuclei were present, all of them in one hemisphere. 
Slightly older eggs examined under reflected light begin to 
show rounded bosses or humpings which appear first at one 
side (no doubt the side towards which the fertilized nucleus 
lay), and afterwards extend all over the egg-surface. ‘They 
soon become better defined and separated from one another 
by linear furrows. Segmentation of the egg-mass is In progress, 
and serial sections show that each hump is the outer end of 
a large more or less conical cell the apex of which is directed 
centrally. The whole egg increases slightly in size, and a small 
