15 



ed larva is somewhat less than .25 mm. lonr. In 12 days 

 it has attained a length of about 3 mm.; 16 days, 6 mm.; 

 20 days, 11 mm.; ?0 days, G3 mm., and S6 days, 100 mm. It 

 is thus seen that v/ithin two v^ecks from the time it has 

 settled, the "Ship-worm" has increased hundreds of times 

 in size, and in five weeks, thousands of times. Within 

 tv;o v;eeks it has changed to a real "Hhip-worm", and even 

 in a month specimens may contain ripe sexual elements, 

 thougli normally these are retained till larger quantities 

 of sperm and eggs are stored for extrusion at one time. 

 I shall describe later what appears to be a change of sex 

 from males to females, the male sex being developed in 

 yoting specimens. I have found males four v/eeks old gorged 

 with ripe sperms, and in every way adult. 



The ages of larger specimens I have been able only 

 to estimate, from the time the piles and other \vooden 

 structures from which they were taken, had been in the wa- 

 ter. In one case I took specimens four feet long and an 

 inch in diameter at the anterior end, from piles that had 

 been in the water less than two years. This was in July, 

 and in this case it seems the "\ orms" had entered the wood 

 not earlier than the spring of the preceding year, and 



