The European Pileworm, a Dangerous Marine Borer 9 



layer of white shell which acts as a further protective covering for the 

 animal, and also prevents any injury to the soft part of the body 

 through contact with splinters of wood. The burrows of older borers 

 are quite heavily lined with smooth white shell. It is an interesting 

 fact that no matter how closely the marine borers may be crowded 

 together, their burrows never run into each other, though the walls 

 of wood separating them may be thin as tissue paper (fig. 6). 



Pileworm Breeds Rapidly 



An astonishing fact in the life of the pileworm is the rapidity with 

 which it becomes sexually mature and begins to breed. The oyster in 

 New Jersey does not usually breed until it is 2 years old, while clams 



Fig. 6. Pieces of Cypress From Platform Riddled by the 



Burrows of Teredo navalis 



Note the white shell which lines the burrows 



require from 1 to 2 years to reach breeding age. As compared with 

 this, Potts (6) found at Samoa, in the Pacific Ocean, with tempera- 

 tures of the water ranging from 80 to 86° F., that Teredo navalis be- 

 came sexually mature within 24 days of the time it entered the wood. 

 The shallow coastal waters of this state are often warmed to 80° F. 

 and above, during the summer, so that growth almost as rapid may 

 occur here. 



In Barnegat Bay, N. J., breeding teredos have been found in less 

 than 6 weeks from the time they attached themselves to the wood, 

 and when they averaged only 3/5 inch in length. In Teredo navalis 

 the eggs are fertilized within the gills of the female by spermatozoa 

 thrown out through the excurrent siphon of a nearby male, and enter- 

 ing with the stream of water passing into the incurrent siphon of the 



