252 MR. A. T. WATSON ON THE STRUCTURE 
water ; but these latter worms have a pore upon the head, which 
appears to be wanting in the earthworms.” He adds that 
“ Dr. Michaelsen has thought that the head-pore serves to relieve 
the brain-pressure—to act in fact as a kind of safety-valve for 
the liberation of superfluous fluid” (26. p. 349). From what 
we know of the habits of the Ammocharide, it is clear that if 
ever such provision be needed, it would be in their case. But to 
continue my notes:—For several days a large Italian specimen 
in the desired condition was under observation, and it was 
noticed that the number of ova in the segment varied, increasing 
and diminishing, and extending even into the bases of the 
branchiz, and ultimately almost entirely disappeared, without 
any apparent cause. Occasionally a considerable number were 
congregated near the centre of the groove in the cephalic lobe, 
and it was expected that a discharge would take place at that 
point, but nothing of the kind occurred. The observations and 
sections, therefore, simply show that, at the point indicated, there 
is an opening into the ccelom, guarded by a network of muscular 
fibres (some of which may be free, protrusible processes), and 
the ova may be either aerated at that point, or make their 
escape there under compression or when disintegrated. As to 
which is the more likely, I will not venture to say, though the 
ova which reach this spot are, apparently, so few that it cannot 
be supposed that all in turn pass into this segment and return 
to the “abdominal” segment, though this is possible. The 
emission of ova from the “ epithelial canal’ was watched for in 
vain; in fact, only once did a worm emerge sufficiently for 
its tube to expose the opening of these ducts, though, when re- 
burying the tubes, it sometimes happened that a sufficient 
length lay naked in the sand. 
Fortunately, the solution came at last. On the evening of 
May 23rd, 1898, a large living specimen from Naples, which had 
settled in a small aquarium, protruded from the anterior end of 
its tube about 20 mm. of the posterior portion of its body, and 
for the space of about ten minutes discharged spermatozoa in 
two white, smoke-like streams, which issued from tubular open- 
ings on the ventral wall (right and left) of the anal extremity. 
During the discharge the animal waved its tail-end vigorously 
from side to side, thus assisting dispersion. The cloud of 
spermatozoa at first settled down, as a white layer, on the 
surface of the sand, but in the course of about half an hour 
