Figure 8. Depth record taken with a Benthos depth-time recorder showing vertical cycling 

 of towed Tucker net. A, cycling amplitude is reduced at shallower depths; B, cycling 

 amplitude increases at greater depths. Distance between two concentric lines .- 250 TCI', 

 time for one entire cycle of chart, about 4 hours. 



Rate of Gas Production 



Direct evidence for rate of carbon monoxide pro- 

 duction in other than surface -dwelling siphonophores is 

 largely lacking (see, however, Appendix C). Nevertheless, 

 a few observations have been made which provide limited 

 indirect evidence. 



Jacobs, in 1937, observed living intact specimens 

 of N. bijuga, captured at Naples, performing a vertical 

 cycling movement when placed in glass cylinders. This 

 was accomplished by active expulsion of a bubble of gas 

 from the pneumatophore by the siphonophore, whereupon 

 it would sink to the bottom of the vessel. Within 45 to 9 

 minutes the colony had refloated itself; then it would again 

 expel a bubble, sink, and perform the entire cycle again. 

 This behavior was observed by Jacobs to continue for a 

 matter of hours. 



Pickwell and others observed a similar phenomenon 

 with the automatized floats of N. bijuga captured off 

 San Diego. Some pneumatophores which had been degassed 

 by gentle suction and set aside in a syringe of seawater 

 containing no gas phase were observed to refloat themselves, 



20 



