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PACIFIC SCIENCE, Vol. IX, July, 1955 
surface during the night. He also notes that 
whereas Dantan thought Tetraplatia must live 
near the bottom many specimens have been 
taken at distances several thousands of meters 
above the bottom. 
As long as Tetraplatia was known from only 
the Mediterranean Sea it was thought of as 
an animal of rather regular seasonal occur- 
rence. Viguier (1890) found it to occur from 
December to April and Carlgren (1909) re- 
ports that he was informed by letter that the 
season at Messina was from January to the 
end of July. The "Valdivia” material from the 
Indian Ocean was collected in February and 
March, while the "Meteor” specimens from 
the Atlantic were collected in March, April, 
July, October, and November. Carlgren’s 
specimen of T. chuni was collected in Novem- 
ber. Although the Mediterranean specimens 
still seem to appear only seasonally this is not 
true of the Atlantic material, which would 
appear to be present in all seasons. In the 
Pacific Tetraplatia has been found in samples 
taken in every month except January and 
presumably is present at all times of the year. 
Thus the problem remains of the apparent 
seasonality of occurrence in the Mediterra- 
nean and the apparent lack of seasonality in 
the Atlantic and Pacific, although samples 
from the latter two areas are too scanty to rule 
out seasonal periods of maximal and minimal 
abundances. 
Most of the reports on Tetraplatia have 
dealt with it as a morphologic and systematic 
curiosity and very little is known of it as a 
living animal, except for the early studies of 
Busch, Krohn and Viguier. Dantan (1925) 
seems to have been the only recent worker to 
have studied it alive. The foregoing studies, 
however, give much information on its mode 
of swimming and the curious writhing move- 
ments which it undergoes, and the numerous 
excellent figures of Viguier (1890) show quite 
adequately the many shapes this medusa may 
assume. One interesting fact relative to the 
living Tetraplatia was the report by Viguier 
(1885) that the refringent bodies (statocysts) 
were spontaneously luminescent and that they 
gave off a blue light. In his 1890 report, how- 
ever, Viguier, after repeatedly seeking to con- 
firm his earlier observation on the lumines- 
cence of the statocysts and having failed, 
suggests that what he observed may have 
been the result of the beginnings of the de- 
composition of the statocysts. 
OBSERVATIONS ON PACIFIC MATERIAL 
The 211 specimens of Tetraplatia which 
have been taken in the eastern Pacific have 
all been identified as T. volitans Busch. These 
specimens have an average size of 4.2 by 1.6 
mm. and a range of from 1.0 by 0.6 mm. to 
9-5 by 2.0 mm. The ratio of length to width 
approaches 1:1 in small contracted specimens 
although it is about 2:1 in most specimens 
less than 2.5 mm. long. Specimens of 3 mm. 
length and longer commonly have a length - 
/Q5° 
Fig. 4. Distribution of Tetraplatia in the eastern 
Pacific. Shaded area enclosed by dashed line indicates 
area from which Tetraplatia has been collected. The dot 
at A indicates the position from which the most south- 
erly specimen was obtained, the dots on the dashed line 
represent the positions of collection of specimens which 
delimit the area within which most of the material was 
collected. 
