44 
a series of bristles, on the first segment there are about 9 on each 
side, on the remaining segments the bristles diminish in size and 
number posteriorly. 
The early stages of this worm have been dealt with by A. Agassiz 
in the Annals & Magazine of Natural History, Vol. xix., ser. 3, 
1S67, page 203, the figures given representing lame from about 
five days old and upwards. In the course of his remarks he 
refers to a work by Claparcde (Beobachtungun) which is not 
obtainable in Sydney, and states that his examples were con- 
siderably more advanced than those figured by Claparede, 
“ having already lost, if ever they possessed them, the bunches of 
ringed bristles so characteristic of the younger stages of many 
Annelids. 7 ’ I may say that the only bristles seen by me were 
the lateral tufts already mentioned. For the first six days the 
larva; swim about vigorously, after which they begin to settle 
down, and appear to be in search of some suitable place to com- 
mence life in earnest. At this stage it is very difficult to transfer 
them from one vessel to another by means of the dipping tube, 
from the fact that the moment they feel the current of water, 
they suddenly fix themselves on the sides of the tube, and no 
amount of shaking will move them. They hold on to the glass 
by the head with leech-like tenacity, whilst the rest of the body 
moves up and down with the water. The only way to get them 
on to a glass slide is to wait until they settle down to the bottom 
of the tube. This peculiar habit of being able to fix on an object 
suddenly, when caught in a current of water, is a very important 
factor in enabling the worm to select any spot it chooses for its 
abode. If the place first chosen is not convenient, it can move 
to another more favourably situated, even in the face of a strong 
current of water. 
In the early part of this report I mentioned the fact that the 
attacks of the worm are usually confined to the anterior and 
posterior margins. The reason for this is obvious. The main 
current of water drawn in by the oyster enters at the anterior 
margin, and passes out at the posterior margin. It is evident 
that if the worms possess the power of selecting their future place 
of abode, those which fix on the anterior margin will benefit by 
being situated in the inflowing current, which is a means of sup- 
plying them with food ; and those fixing on the posterior margin 
will also be similarly benefited, only in a lesser degree. 
From what E have seen of the habits of the young worm 
in its free swimming state, and also of those already men- 
tioned as having just settled down, I am of opinion that the 
young worm simply swims into the open oyster, and fixes itself 
by its head on the margin of the shell. If the position is 
suitable it immediately begins to construct a tube and collect 
a large quantity of mud. Jt may possibly be guided to the 
