
No.427.] C@LENTERATE FAUNA OF WOODS HOLE. 553 
this station, is not specially abundant. Its season is compara- 
tively brief, ranging from April 12 to May 5. While sometimes 
quite abundant at certain localities, its hydroid phase is as yet 
unknown, as is also its development. 
Trachynema digitale A. Ag. This Trachomedusa is occa- 
sionally taken here in considerable numbers in April, but is not 
a common medusa. Little appears to be known as to its habitat 
or life history, but it is probably more or less pelagic, and 
hence subject largely to the influence of ocean currents, etc. 
Rhegmatodes tenuis A. Ag. Note is made in this connec- 
tion of the occurrence of this medusa in large numbers during 
the summer of 1900, the first record during several years, 
and its utter absence during the present season. It is usually 
recognized as a summer medusa, and the present record only 
confirms this. What is more specially worthy of note is the 
erratic aspect of its appearance, apparently at long intervals, 
and then usually in great numbers, indicating seemingly some 
local or environmental condition as governing its occurrence, 
rather than purely seasonal mutations. Were Rhegmatodes 
a pelagic medusa we might account for mutations of this sort 
through the agency of shoreward currents or winds, as often 
happens with Physalia, and perhaps also with Trachynema, 
as intimated above. But so far as I am aware, this medusa, 
in common with most of the Hydromedusz, is more or less 
restricted to the littoral fauna, and hence only incidentally 
affected by such influences. This is another medusa whose 
hydroid yet remains unknown. Possibly when its life cycle 
is fully known the apparent capriciousness of its occurrence 
may be cleared up. 
Staurophora laciniata A. Ag. was likewise taken in consid- 
erable numbers in early May by Mr. George M. Gray, and 
later in the month by Dr. H. M. Smith. So far as my records 
are concerned, this is the first occurrence of this medusa in 
several years at this station. One of its peculiar structural 
features, the early confluence of the oral lobes with the frills 
of the gonads, so that they can only be distinguished with 
difficulty, was described by A. Agassiz. No mention, so far 
as I am aware, has been made of the origin of actinulz in this 
