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, 

 1867, page 203, the figures given representing larvre from about 

 five days old and upwards. In the course of his remarks he 

 refers to a work by Claparede (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." I may say that the only bristles seen by me were 

 the lateral tufts already mentioned. For the first six days the 

 larvje swim aV)out vigorously, after which tlu^y begin to settle 

 down, and appear to l)e in search of some suitable place to com- 

 mence life in earnest. At this stage it is veiy ditficult 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 curi'ent of water, is a very important 

 factor in enaljling 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 eai'ly 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 

 curreiit 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 po.ssess the power of selecting their future place 

 of abode, those which fix on the anterior margin will benefit \>y 

 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 lessi^r degree. 



From what I 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. It may possibly be guided to the 



