546 Phylum Mollusca 



number of worms. It is not difficult to secure a complete series of 

 developmental stages because the shipworm is remarkably prolific. 



The embryos are retained in the gills about two weeks and are then 

 expelled into the sea as actively swimming veliger larvae. The free- 

 swimming larvae feed upon diatoms and grow for approximately two 

 weeks longer, then settle upon wooden structures, metamorphose, and 

 burrow into the wood. One month after metamorphosis the young 

 Teredo measures % inch in length. In six weeks it measures 1% inches 

 and becomes sexually mature. The first eggs produced by these young 

 shipworms are spawned about August 20. 



It is an easy matter to collect well developed veligers from the parent 

 worm and keep them in healthy condition in aquaria by feeding them 

 diatoms. It is possible to study every phase of the life history of 

 Teredo by these methods, including the rate of growth.* 



♦For a more complete account of the natural history of Teredo navalis see Biol. Bull. 

 55:260 and 65:283. 



Editor's Note (see p. 538): According to recent investigation by the U. S. Bureau of 

 Fisheries incubation period in Delaware Bay varies from 18 to 53 days. P. S. G. 



