contained within the pneumatophore is of paramount im- 

 portance in estimating the total amount of gas which must 

 be secreted to maintain float volume at various depths. 

 Determination of volume of enclosed gases compared to 

 volume estimates made from dimensional measurements may, 

 in addition, allow some estimate of total number of bubbles 

 expelled during an upward migration. 



It can be seen from figure 7 that gases contained in 

 nanomian floats more closely approximate a prolate sphe- 

 roidal shape than do the floats themselves. Calculations 

 of gas volume based upon linear dimensional measurements 

 might therefore be expected to indicate more accurately 

 the true volume of the gas bubble than similar calculations 

 based upon float dimensions (see Appendix C). 



* 





Figure 7. Specimens of Nanomia bijuga, photographed 30 days following formalin fixa- 

 tion. The stolons are contracted and most members of the colony have been shed. In 

 general the enclosed gas bubbles more closely approximate a prolate spheroidal shape 

 than do the external dimensions of the floats themselves. (Magnification, approximately 

 12x.) 



16 



