was hindered by the light given off. That this condition can continue 

 over a series of nights is indicated hy the report of observers on 

 board the SS PORT irUNTER during the nights of l8 - 21 August I925. 



"Extraordinary phosphorescence was noted in the sea. 

 The sea became luminous from horizon to horizon each evening 

 between 8:30 and 9:00 p.m., and disappeared in the morning 

 about an hoiur before daylight. It gave the effects of the 

 ship sailing in a sea of milk, at times very bright, and 

 it was possible to read the Azimuth Tables on the bridge 

 by the light, usually between the hours of 2 and h a.m." 



Bioluminescence in this area appears to occur much less freq.uently 

 south of the Equator than north of it. Reports south of the Equator 

 make up only about lOfo of all those available north of 60 S. All 

 three types of displays have been observed, the glowing-ball and spark 

 types of bioluminescence being predominant. Shoals of pyrosomes or 

 salps are responsible for most of the glowing-ball bioluminescence in 

 this region. The few reports available indicate that glowing-ball 

 biolujninescence has been observed most frequently in the period April 

 through June and again from October through December. Little is kno-^-ra 

 about the incidence of spark-type biolmninescence, but there is 

 probably an increased number of these displays in the direction of the 

 Antarctic Convergence, where euphausiids and copepods reach peak 

 abundance most likely in the saime months as do the glowing-ball 

 organisms. 



"PHOSPHCRESCEIMT WHEEL" AND "WAVE" DISPLAYS (FIGURE 8) 



Reports of 85 "phosphorescent wheel" displays and 26 "wave" dis- 

 plays (not plotted) are on file at the Oceanographic Office. The 

 category of "wave" displays Includfes such light formations as luminous 

 undulating waves, luminous rays extending through the water, and various 

 light patterns which cannot be categorized as "phosphorescent wheels." 



Descriptive material concerning "phosphorescent wheel" and "wave" 

 formations is both voluminous and variable. The complexities encountered 

 in attempting to classify such appearances are illustrated by the follow- 

 ing two reports from "The Marine Observer." 



MV SCOTTISH EAGLE. Captain R. R. Baxter. Bandar Maahur to 

 Kwinana. Observer, Mr. S. M. Grant, Chief Officer. 



"23rd April, 1955;> 1625 to 1635 G.M.T. When approaching 

 Jazirat Tunb Island a bright flashing light was observed 

 on the port bow, distant about 1 mile. Almost simultan- 

 eously another was observed on the starboard bow. On 

 approaching it was seen that these were two revolving 

 phosphorescent wheels. The ship passed between them, 

 the centres being about -5- mile distant on either side. 

 The wheel on the port side appeared to revolve anti- 

 clockwise, and that on the starboard side clockwise. 



38 



