3io 



CHARLES ZELENY. 



AttacJiincnt of the Larva. - The period at which attachment 

 of the larvae should take place is a critical one and death is the 

 usual result under ordinary laboratory conditions. In my ex- 

 periments at Cold Spring Harbor, however, there were hundreds 

 of survivors in each jar. On account of the frequent change of 

 position of the jars, as well as the complex refractions and reflec- 

 tions within them, I was not able to find out whether the place 



of attachment of the larvae has any 

 ; definite relation to the source of the 

 light. The young Serpulids were 

 found to be fairly uniformly distrib- 

 uted, though there were groupings 

 at several different places. One of 

 these consisted of a large number 

 collected on the glass just below the 

 surface film of the water. These 

 formed a band surrounding the jar, 

 but it is interesting to note that 

 they did not grow as rapidly as 

 those lower down, although fresh 

 sea water was added in each case 

 to raise the level slightly and make 

 up for evaporation. Going down 

 from this band-like zone of greatest 

 frequency the number of individu- 

 als decreased until the bottom of 

 the vessel was reached, where again 

 there was a considerable number, 

 especially in the corner between the 

 bottom and the sides of the jar. 



Tube Formation. The tube 

 when first formed is a very narrow, 



almost transparent ring of calcareous matter, the body of the 

 short larva extending out of it at both ends. This ring is 

 secreted by the region just back of the free anterior end of the 

 thoracic membrane and as its formation goes on the animal can 

 be seen to extend its thoracic membrane over the anterior edge 

 of the tube in order apparently to smooth the edges and get the 





FIG. i. (X4-) Agroupofthe 

 young of Hydroides dianthus as at- 

 tached to the side of a battery jar. 

 The level of the water surface is 

 shown, a and b are groups showing 

 radial divergence of the tubes, c 

 shows two tubes which have evi- 

 dently responded to a lateral stimu- 

 lus. No definite relation to gravity 

 is shown. 



