Mr Potts, The Swarming of Odontosyllis. 193 
The Swarming of Odontosyllis. By F. A. Ports, M.A., Trinity 
Hall. 
[Read 10 February 1913.1 
THROUGHOUT the months of June and July in 1911 I had 
frequent occasion to take and examine dredgings from the sea 
bottom outside the harbour of Nanaimo, British Columbia. The 
bottom deposits there are of a peculiar character, consisting largely 
of the debris of dead Hexactinellid sponges. The long interwoven 
spicules form a matted mass which furnishes a secure retreat for 
many species of Polychaet worms. One of the most abundant and 
interesting of these is a species of Syllid which proved to be 
Odontosyllis phosphorea described by Moore* in 1909. During 
the whele period the worms of this species contained reproductive 
products. The females were of a bright red colour due to the 
egos, while the males showed the natural yellow colour and trans- 
verse markings of the species. Both sexes were very irritable 
under handling and broke up entirely when attempts were made 
to fix them with sublimate solutions or alcohol, and at the same 
time an intense phosphorescence was produced. 
No appearance of the mature worms at the surface was noticed 
during these months, though a close lookout for phenomena of 
this kmd was maintained. On August 15th, however, Professor 
McMurrich of Toronto informed me that he had observed just 
before sunset hundreds of small worms swimming on the surface 
of the sea in Departure Bay, a shallow inlet adjacent to the 
grounds described above. Examination of a number of these 
which had been brought into the laboratory showed me that they 
belonged to the species found so abundantly amongst the sponge 
debris. 
The next night Professor McMurrich and myself followed the 
phenomenon as closely as possible. Sunset was about seven o'clock, 
and half an hour or more before isolated individuals began to appear. 
At first these were mostly males, but as the numbers increased so 
did the proportion of females to males until there was approximate 
equality. On their appearance from the depths the individuals of 
both sexes swam round and round in circles with swift undulatory 
movements. <A short time after, the movements became slower, 
finally ceasing, and during spasmodic flexures of the whole body 
the eggs and spermatozoa were discharged. Then the spent 
‘Individuals sank slowly beneath the surface. No approximation 
of the two sexes was observed to take place, but my impression 
was that each individual sought the surface without fixed plan or 
* J. Perey Moore, Proc. Acad. Nat. Sci., Philadelphia, vol. rx1. 1909, p. 327. 
VOL. XVII. PT, II. 13 
