JCNE 



ISSo.] 



♦ KNOWLEDGE ♦ 



547 



muscles, which operate thorn like forceps or scrapers, the 

 edges of the shells tearing away little chips or fibres of the 

 wood. The continued scraping m.ikes the walls of the cell 

 regular, and time, with the action of water, polishes them 

 smooth. The bore of the teredo, when examined, is seen 

 to be perfectly round, and the surface free of indentations. 

 It is also generally straight, as the inclination of the worm 

 is in the line of the grain of the wood, and is diverted only 

 when the course will project it into the tunnel of some 

 other borer, or when the path leads through hard knots 

 or twists in the wood. The accompanying engraving of 

 the worm (Fig. 1) is about two thirds of the present size 

 of the preserved specimen from which it was made. The 

 latter was kindly furnished the L u mbermaji hy Mr. J. W. 

 Putnam, of the creosote works at West Pascagoula, Miss. 

 It was taken from timber which had been in an arm of 

 the Gulf of Mexico one year, and was 12 in. long when 

 aecared, Feb. 21, 187S. 



Fi-. 1. 



It is remarkable with what accuracy the teredo avoids 

 the buiTow of its neighbour. There may be hundreds of 

 worms living in the same cubic foot of timber, but they 

 never, even by accident, cut across or into the cavities. It 

 is net known whether in this they are guided by the touch 

 or the hearing, probably both. Coming in contact, during 

 its boring, with wood having obnoxious qualities, the worm 

 avoids it by going around, or it will back down a third of 

 its length, and begin a branch tunnel, previously building 

 a calcareous dam across the abandoned portion of its cell. 

 It will cut within the least possible distance of its fellowit, 

 or within a hair's width of the outside of the timber, with- 

 out breaking the division wall. 



Continuing the description of the teredo, however, one 

 will find, just at the base of the cutters, the esophagus or 

 orifice leading into the stomach, in which can be traced 

 the fine sawdust and chips, showing that the worm feeds 

 upon such matter. This is more likely to be food for the 

 worm than the debris of stone which the shell-fish (Litko- 

 phagi), of the same group as the teredo, have tc swallow in 

 the course of their cutting operations. An intestinal canal 

 about the sixteenth of an inch in tUameter in adults, and 

 continually growing smaller, extends from the stomach to 

 the inferior extremity. The stomach itself is a dark-looking 

 sac, nearly of the diameter of the teredo, and situated a 

 short distance from the " head." Whether the worm has 

 even a rudimentary brain or spinal chord, and consequently 

 a real thinking, commanding brain, is not certainly known. 

 It is almost transparent, and its interior arrangements can 

 be plainly seen when it is suspended iu glycerine or alcohol, 

 but outside of the viscera above mentioned, there is nothing 

 of importance visible. The smaller end of the teredo is atr 

 tached to the shell IiLing by a membrane in the shape of a 

 sleeve which closes the entrance hole and prevents water 

 from coming into the cell. This sleeve is provided with two 

 long appendages, file like, which it protrudes, by muscular 

 action, out of the aperture. This is partly an instrument to 

 aid in the removal of the rough and unyielding debris of the 

 wood cut by the worm, and partly a weapon of defence 

 against enemies. Without some such protection a rival 

 teredo or some parasite covdd enter the tunnel and devour 

 the inmate alive. 



The teredo having lived its span, given birth to millions 

 of young ones, closes the outer aperture with a coating of 



lime, entombs itself, and dies. Often, however, death comes 

 before the allotted time, for so many worms will cuter a 

 piece of timber as to eat it up. Tlie whole community, 

 having no future means of subsistence, dies of starvation. 

 Logs have been found cut all to iiieces, and filled with lialf- 

 grown worms all dead. Sudden death also comes sometimes 

 from floods of muddy fresh water. When the Mississippi 

 River broke through Bonnet Carre crevass, muddy river- 

 water flowed through Lake Pontohartrain and Lake Borgne 

 into Mississippi Sound, driving out the salt water as far 

 east as Pass Christian, and the teredos were killed in great 

 quantities. It seems the worm withstands clear fresh-water 

 very well, for at Brisbane, Australia, it is forced to survive 

 the annually recurring exposure to fresh water, lasting from 

 two to three months. 



Drying iu their cells, the sea water soon penetrates the 

 lime blockades and dissolves the glutinous mass. The shell 

 lining washes out in a few months, and a smooth and grace- 

 fully-curved hole remains, a monument of the destructive 

 work of the Teredo tiavalis. 



As previously intimated, the teredo may be found in all 

 quarters of the globe, but its ravages are greatest in the 

 warm waters of equatorial seas. This is accounted for by 

 the fact that the summer season is the time of activity for 

 these worms, and the season lasts longer in the southern 

 waters. The teredo has appeared with destructive eflect 

 in colder climes, however. It is recorded that in 1731 

 and 1732 it suddenly appeared in prodigious numbers in 

 Holland, and threatened the country with inundation by 

 devouring the piling of the dykes. The worm bores in 

 any kind of timber, in soft as well as hard, except 

 that of trees of evergreen growth like the palmetto 

 palm. Its work is very rapid. Boats and barges have 

 been sunk in a few days by the penetration of the 

 shells, and solid piles, 12 in. or 1-5 in. in diameter, have 

 been cut so completely away as to break of their 

 own weight and fall down within .six months of the time 

 they were placed in the water. A piece of timber which 

 is completely worm-eaten will preserve its outer surface 

 perfect up to the moment it falls. Close examination of 

 such a sample of wood shows that in the outer surface are 

 innumerable holes about the size of a pin. These are the 

 entrance holes of the teredo ; break the wood and it is 

 found honeycombed in cells of from a half-inch to twenty 

 or more inches in length, as indicated in the engraving 



Fig. 2. 



(Fig. 2), which was made from a section of what appears 

 to have betn a five-inch post, or possibly a telegraph pole 



