lO 



THE MUSEUM. 



supposed the shipworms were natives 

 of India, whence they had been 

 brought by shipping in modern times. 

 During these times they were consid- 

 ered true worms, and it was not till 

 the time of Cuvier that their molluscan 

 characters were recognized. 



"Even if the shipworms were not 

 recognized to be bivalve mollusks from 

 their adult organization, it would be 

 easy to determine this fact from a 

 study of the development. 



"The shipworm starts in its de- 

 velopment as an egg which none but a 

 specialist could distinguish from the 

 eggs of most bivalves. In American 

 forms that seem most abundant; at 

 least in our Southern waters, the eggs 

 are cast freely into the water and soon 

 fertilized by the male element. As 

 soon as fertilized tne eggs begin to de- 

 velop, and in our warm Southern 

 climate become little free-swimming 

 creatures in from three to four hours. 

 It is true that these little creatures 

 have as yet none of the distinctive 

 features of the shipworms, or even of 

 bivalve mollusks. But within a day 

 the bivalve shell is acquired. For a 

 few days one can rear the larva in an 

 aquaria, but after a time the condi- 

 tions become unfavorable and they 

 disappear. For perhaps three weeks 

 more, in a state of nature, they lead a 

 free-swimming life and are gradually 

 transformed into a little free-swim- 

 ming bivalve almost exactly like the 

 little clam or oyster. But how or 

 where in nature this transitional period 

 is passed has not been observed. 



"The next stage which the writer 

 found was the little bivales, about a 

 hundredth of an inch in diameter, 

 crawling over the surface of the wood 

 in quest of places for their future 

 homes. Once they have found appro- 

 priate places they begin to change. 

 One by one the bivalve characters 

 are lost, and the little bivalves are 

 transformed into the very long, worm- 

 like creatures which are found in 

 wooden structures in salt water the 

 world over. 



"But along with the transformation 

 the bivalve shell is preserved, though 

 it is much modified as compared with 

 other bivalve shells, and covers only a 

 small part of the head end of the body. 

 With it the shipworm excavates the 

 burrow in the wood in which it lives, 

 and seems able to penetrate the hard- 

 est or softest kinds of wood with equal 

 facility. As the wood is grated away 

 by the shell the small particles are 

 taken into the digestive canal and the 

 debris is extruded through the anus; 

 but whether in serves for food in any 

 way is a question in dispute. During 

 its life in the wood at least the larger 

 portion of its nutrition is taken in 

 through the tube that hangs at rest 

 in the water, and consists of small 

 animal especially vegetable organisms. 

 "In thinking of shipworms, then, it 

 should be remembered that the wood 

 in which they form their burrows is 

 primarily for their own protection, 

 their long, naked, delicate bodies 

 being perfectly defenceless. 



"At Beaufort all kinds of unprotect- 

 ed wood becomes literally riddled in a 

 very short time. There are two kinds 

 of worms found there /n great and 

 about equal abundance. 



"These are the Teredo nonvegica 

 and Xylotra fimbriata, whose mode 

 of spawning has been already des- 

 cribed. However, a very small pro- 

 portion of specimens were of Teredo 

 navalis, one of the common European 

 forms. In this species the eggs are 

 retained in the gills of the mother 

 during a considerable period of their 

 development, perhaps almost till time 

 for them to set into the wood. It is 

 apparently this last species which the 

 writer has found most abundantly in 

 Long Island Sound, though a con- 

 siderable portion of Zylotra fimbriata 

 were also found. 



"The breeding season in North Car- 

 olina, so far as determined, lasts at 

 least till the middle of August, and 

 perhaps throughout the summer. That 

 the latter is true is indicated by two 

 sets of facts. In the first place, in- 



