Gatty Marine Laboratory, St. Andrews. 183 
The posterior hooks do not differ essentially in structure 
or arrangement, though they are smaller. 
Reproduction —An example procured off North Unst by 
Dr. Gwyn Jeffreys in July had a series of ova in a hollow on 
the ventral surface behind the anterior region. 
The tube is of great density, slightly translucent or 
vitreous, and has anteriorly a sharp dorsal spike and two 
infero-lateral spikes. A serrated keel runs along the mid- 
dorsal line, and the tube is fixed to shells, stones, or other 
submarine bodies. The inner surface is smooth and vitreous, 
and the minute teeth along the anterior edge of the hook 
must be of great hardness. Whilst the initial coil is adherent 
the distal end stands up freely in many cases. When densely 
grouped on stones the tubes are less rough and the aperture 
is smoother, and as they are coiled and interwoven, with their 
ends often free, a considerable change takes place in the 
facies of the tube. It still retains its median ridge, but in 
a modified form. The whole aspect of the mass is in con- 
trast with the ordinary conditions of the species. Yet here 
and there at the edges the usual aspect.is observed. ‘The 
examples indicated came from the deeper water off St. An- 
drew’s Bay, attached to sandstone and accompanied by the 
tubes of Sabellaria. 
In Apomatus ampulliferus, Phil., the seventh form, the 
collar is less developed than in Placostegus, but though 
narrower it is thicker and follows a similar arrangement, 
as starting from the dorsal edge of the fused collar and 
alar membrane it passes as a continuous fold across the 
ventral aspect to the opposite side. The truncated anterior 
end after removal of the branchize presents a somewhat 
rounded central elevation with a fossa between it and the 
coliar. 
The branchie are reddish in life and are seven in number 
on each side. They are of moderate length, somewhat soft 
and thick, and in the preparations are usually coiled and 
doubled. The broad filaments taper slightly toward the 
extremity, and end in a subulate process, the pinnz 
extending almost as far, so closely do they approach the 
tip. The tissue of the filaments is lax, so that doubling 
readily occurs, and both they and the pinnz have hypo- 
dermic glandular cells, the tissue of the ciliated pinne 
being especially soft, one moniliform blood-vessel being 
conspicuous. Instead of the firm hyaline cuticle of other 
