Serpididae 185 



feeding. The larvae will consume very readily small diatoms which are 

 then added to the culture. For this purpose it was found that species 

 of Navicula and Nitzschia [See p. 34.] were of suitable size. They were 

 eaten in large quantities. The larvae grow rapidly and when they have 

 developed 6 or 8 segments they form mucous tubes within which they 

 hide themselves. When the larvae reach an age and size having 10 or 

 12 segments they will consume other food in addition to diatoms. At 

 this time Ulva and brown kelp, such as Nereocystis, may be added to the 

 diet. At this time they may consume other small worms and any mate- 

 rial that they can devour. The worms extend themselves almost their 

 entire length from their tubes and reach for food. 



After the young worms develop tubes it is not necessary to change the 

 water so frequently. A change every 2 or 3 days is sufficient, and at a 

 later date, once a week will suffice, provided there is plenty of green 

 vegetation in the water. 



Several important factors must be kept in mind: 1) there must not 

 by overcrowding of organisms; 2) fresh water must be provided to 

 allow for a sufficient supply of oxygen; 3) care must be taken to prevent 

 contamination; 4) the temperature must be kept within a limited range; 

 and 5) a sufficient quantity of suitable food must be provided at all 

 times. 



Order polychaeta sedentaria 

 Family serpulidae 



HYDROIDES HEXAGONUS 



Benjamin H. Grave, De Pauw University 



Hydroides hexagonus, a serpulid worm, secretes a calcareous tube 

 which adheres firmly to shells of mollusks, stones, and wooden structures. 

 The breeding season at Woods Hole opens between June 10 and June 15 

 and closes between October 15 and November 1. 



METHOD OF OBTAINING EGGS AND SPERMATOZOA 



To obtain eggs or sperm it is advisable to remove the worms from 

 their calcareous tubes and place them in stender dishes or Syracuse watch 

 crystals filled with seawater, one worm per dish. When so treated they 

 always spawn immediately if they are sexually mature. The sexes are 

 separate and the gametes, whether eggs or spermatozoa, are carried free 

 in the coelomic cavities from which they are extruded through nephridio- 

 pores located along the sides of the body. During the early part of the 

 breeding season over 50% of the spawned eggs are immature and under- 

 size. Later on they are nearly all mature and fertilizable. Maturation 



