stralimi. 'I'lic .siiii|>li' I'-lonii is i)lU-n iuoMilif'd iu Uilmn lliat <x:<.ur in hIjojiIi* 

 of Hand ami slu-lls. Tli«; ariiiH juay here Im? k<> coiixtruf.-teii that they turn 

 abi-uptly aside from lar^^e shells that are in their way. Tulxts with thn*** 

 arms are frei^uently found (I'iii. 4). These are tubes that have been en- 

 larged liy the extension of the horizontal jiortion and the formation of 

 a new (vertical^ arm. A septum at the base of the interm«?diate arm s<;p- 

 arates its eavity from ihat of the horizontal j»ortion. I liuve found Inter- 

 me<liate arms with little or no sand, some completely filled, while many 

 have begun to macei'ate. Every larg«? tub*; bears the shreds of one or more 

 of these macerated interme«liate arm.s, or the ereseentic s<.-ars that mark 

 their former union with the newly formed extension. 'J"he annulations 

 near the (jrificfs and tbo longitudinal strips of thinner, sand-covered, parch- 

 ment alternating with the thicker |>ortion of the tubes rei)res«,'nt successive 

 steps in the formation and enlargement of the tul>es. 



'J'here is -.^reat diversity in the size of the tuU;s. A very young worm 

 forme«l a characteristic I -sliaix,'<l tube ihnn; millimeters in diameter at its 

 wider jiortion. and one and three-fourths millimeters at its orifices. The 

 di.stance between the orifices measui'ed fourteen and one-half millimeters, 

 and the length of the arms (measured from the lower side of the horiz^^ntal 

 portion to its bas<:?) was sixteen millimeters. I liave collected tubes which 

 ranged in lengtli from six to fifty centimeters and with arms six to twenty- 

 two centimeters long. 



'I'he formation of the first tube and the subseipient enlargements was 

 obser\-ed on larvae of ('liiU'toj)trin>f rarioiJcd(Jtui< which I was fortunate 

 enough to <ollect in the tow-net. These larvae, wiiicli were transforming 

 from the free-swimming mesatrochae into the creeping in<lividuals, were 

 kept in aquaria of sea watej- well stfx,-ke«i witli diatoms. When the larvae 

 move among the diatoms they leave a trail of mucus that cements the 

 sand and diatoms together. Later they niake short, horizontal, mucus- 

 coated tunnels into the mass of «liatoms and sand. One of these tunnels 

 may be extended to several times the length of the b^xly and from this 

 simple tunnel of agghitinated sand and diatonis the larvae may build the 

 tube within which it subsi-ijuenJly remains confined. 



The first tul>e in wlii<!i the larvae lives and fe<'<Ls for .several days 

 is neiirly a millimeter in diameter and from eighteen to twenty-two milli- 

 meters long. It is either a .straight tube or a shallow T.' whose curved 

 portion is downward. 



[0— 18192J 



