Phylum IX 



Bryozoa, Class Ectoprocta 



BUGULA FLABELLATA AND B. TURRITA 



Benjamin H. Grave, De Pauw University 



THE breeding season of these Bryozoa at Woods Hole, Mass., extends 

 from June i or June 15 to Nov. 1. 



The complete life history of Bugala flabellata is readily observed 

 because of the ease with which larvae are obtained and kept under 

 laboratory conditions until colonies of several individuals are established. 

 The larvae, which resemble the trochophores of annelids, are given off 

 by the parent colonies at dawn. To obtain them in abundance sexually 

 mature colonies should be collected late in the afternoon and placed in 

 dishes of seawater. These are left over night near a window. Larvae 

 issue from the colonies early in the morning and continue to be liberated 

 from 5 to 10 a.m. They promptly swim to the lighted side of the dish, 

 where they may be taken in a pipette and transferred to fresh dishes of 

 seawater for study. Finger bowls or stender dishes are recommended 

 for the purpose. 



At first the larvae, as indicated above, are strongly and positively 

 heliotropic but later a change occurs and they become negative in their 

 response to light. Still later they make permanent attachment to the 

 walls of the dish and proceed to develop into colonies. The larva re- 

 quires no food because it has no digestive tract, but as soon as attachment 

 occurs the containing dish should be placed in running seawater to secure 

 aeration and food for the developing colony. 



The swimming period of the larva is about six hours in duration. The 

 first individual of the colony becomes a complete feeding polypide within 

 two days and a colony of eight is established in one week if conditions 

 are favorable. The colonies under natural conditions bud rapidly and 

 become sexually mature in 1 month. They continue to grow for ap- 

 proximately three months which is the approximate duration of life of 

 colonies established early in the summer. Colonies established late in 

 the summer live over winter. 



The rate of growth of colonies may be observed under natural con- 

 ditions from the establishment of the colony to maturity by placing 



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