MONOGRAPH OF AMERICAN SHIPWORMS. 5 



brought in through the incurrent siphon is strained through these 

 organs and by cilia carried forward to the mouth, where they are 

 ingested. 



Shipworms, after they have excavated a comfortable home (see 

 the cutting tools figured on pi. 1, figs. 4-10) and lined this to a vary- 

 ing degree, depending upon the species in question, with a smooth 

 shelly deposit, eventually stop burrowing, but continue to live and 

 feast and reproduce, no one really knows for how long a period. We 

 are told that some reach sexual maturity and may be full size within 

 three months after settling down upon a piece of wood, and we are 

 also told that some may produce as many as half a million to three 

 million eggs, but these are all matters that need to be carefully 

 studied, for as stated at the outset, little, yes, very little, is definitely 

 known about these creatures. 



Another structure of interest in the shipworms are the pallets. 

 These are developed at the tail end of the animal ; that is, the outer 

 end (see pi. 3, a figure copied from Sigerfoos, which gives in a dia- 

 grammatic way the function of these structures). When the ship- 

 worm is actively engaged in feeding, the pallets are withdrawn, as 

 shown in the top figure. The siphons are then extended, the lower 

 one whose distal end is guarded by a series of tentacles that may keep 

 undesirable material from entering this tube, carries the food and 

 oxygen-containing water to the animal. The upper one carries the 

 water away and into this are also discharged the fecal material and 

 the sexual products. If any disturbing factor on the outside of the 

 infested wood presents itself, or when the shipworm so desires, he can 

 withdraw the siphons, push forward the pallets and thus effectively 

 close the door to undesirable visitors, or probably even fluids, until 

 the demand for oxygen compels the mollusk to take in a new supply 

 of water. 



The larval shipworm is free-swimming and attaches itself to 

 wooden structures which it needs for its further development. This 

 further development has been beautifully treated by Sigerfoos for 

 Banhla {BcmkieUa) go^uldi Bartsch, to which anyone is referred who 

 desires to follow this phase of the life history of the animal. 



Some of the problems that suggest themselves to the biologist in 

 connection with shipworms are : 



A. The systematic study which should form the foundation for all 

 other inquiries. This is here attempted. 



B. A study of the range in distribution of the various species, and 

 their relative abundance. 



C. An examination of the physical oceanographic conditions that 

 determine this distribution. 



D. A studv of the life history of the various forms. 



