In an earlier paper (Prandle, 1978b) estimates were made of the monthly-mean residual flows through the Dover Strait for the period 1949–72. This time series has proven to be of some interest to marine biologists (Colebrook, Reid & Coombs, 1978; Reid & Budd, 1979; Taylor et al. 1981). This short additional note extends this time series up to 1980 (Table 1).

Other model studies of wind forcing in this region have been published in recent years.

Commensal copepods were found abundantly in samples of the ascidian Molgula complanata Alder and Hancock taken from experimental panels for histological examinations (see Schmidt, 1982). As little data exists on the possible ecological importance of such association to the ascidian host (Gotto,1979 for review), the incidence of‘ infection’ was quantified in the present study over a period of 8 months.

Between 31 October 1980 and 3 June 1981 specimens ofM. complanata( 6 mm maximum diameter) were removed from panels suspended from a raft in Langstone Harbour, Hampshire; 50–125 individuals per sample. Associated copepods found in the branchial basket were:Notodelphys agilis Thorell,Botryllophilus macropus Canu, andDoropygus pulex Thorell* (cf. fig. 2 in Schmidt, 1982). The former two species occurred sporadically, but the latter consistently. Owing to the relatively large, globular size ofD. pulex (caused by very inflated brood pouches), it almost filled the space provided by the branchial basket of smallM. complanta. Hence,D. pulex was found onlyone per ascidian, although 1–3 juveniles (several copepodid stages) were often present with the adult.

On 31 October 1980,D. pulex was present in 64% of 115 animals examined. It is interesting to note that, despite such abundance,D. pulex has not been reported previously in association withM. complanata (Gotto, i960). On 28 November 1980, the incidence of ‘infection’ was still high (62 %) but thereafter declined (14 January 1981: 35 %; 10 February 1981: 34 %; 11 March 1981: 42 %) to a value of 13 % by 8 April 1981, around which it stayed until the end of sampling (3 June 1981).

Sagartiogeton laceratus Carlgren. was observed in 1979 in large numbers (11–20 m) in shallow water (5 m below chart datum Sullom Voe) at Whaal Firth, Yell, Shetland, at a site named Stany Pund. It was recorded at a nearby site, Poita, at a lower density (1–2 m) in deeper water (6–8 m below CD.), and was also recorded as ‘common’ at the shallow head of the firth.

Very large numbers of Aurelia aurita (L.) were observed within the sheltered, shallow arm of the firth, within the upper few metres of water.

Each year since 1979 the same occurrence has been noted, and in the summer of 1980 the predation of Sagartiogeton upon Aurelia was observed and photographed on several occasions. These observations were repeated in 1982.

Sagartiogeton laceratus is found attached to shell fragments in silt, the column inclined towards the current. During ingestion the tentacles shorten, and the mouth, disc, and column, distend many times their normal dimensions. (Estimated to be 400% for the column, disc.)

It seems likely that the occurrence of both species in sufficiently large numbers to make predation noteworthy is due to the position and depth of Whaal Firth. It forms a north facing ‘trap’ on the eastern side of Yell sound through which ebb and flood tides move rapidly. The total length of Whaal Firth is approximately 7 km of which 4 km are relatively exposed, and 3 km sheltered.

In 1955, Kerkut recorded the spontaneous activities of a tube foot of Asterias rubens L. Such activity consisted of cyclical protraction and retraction phases, one complete cycle lasting on average some 6·5 min (S.D. 2·5). The duration of the protraction phase was on average 4·3 min. It is reasonable to assume that under the conditions of this experiment a similar level of hydrostatic pressure was attained as was found by Binyon (1964), namely 30 cm water. There then followed a fairly rapid retraction of the podium and a quiescent period of some 2·2 min duration. An individual podium would thus execute some 9·2 cycles/h.

Conflicting opinions exist as to the method of feeding employed by Leptopentacta elongata (Dub. and Kor). Orton (1914) and Mortensen (1927) suggested that it may be a deposit feeder. Chia & Buchanan (1969) noted that post larval specimens up to 1 year old deposit fed. Fankboner (1981), in a short study, concluded that the adults were cryptic deposit feeders. Hunt (1925) and Fish (1967), however, observed what they concluded was suspension feeding. All the above observations were the result of aquarium studies. Fish (1967) also demonstrated that Leptopentacta hibernated between October and April or May both in the field and in aquarium. He also observed that hibernation could be induced in the summer months by reducing water temperature to 8°C but that winter hibernation could not be curtailed by raising the water temperature.

Obsevations made by one of us (B.P.) while diving indicate that Leptopentacta suspension feeds. This behaviour has been observed on several occasions from several sites around the Irish coastline with specimens then being caught and their identity confirmed. While feeding the tentacles are held clear of the substrate to intercept suspended material.

These observations clearly do not support the description of Leptopentacta solely as a cryptic deposit feeder, indeed the evidence for the adults deposit feeding at all is weak. Orton (1914) and Mortensen were only speculating on Leptopentacta being a deposit feeder based on the observation that specimens in aquaria spent much of their time completely buried. Hibernation, as shown by Fish (1967), is a possible explanation for this.

Poly dor a ciliata (Johnston) is a polychaete which lives in a U-shaped tube and is found in a wide variety of substrata, ranging from soft clays or muds to hard calcareous materials. Cliona celata Grant is a siliceous sponge which inhabits tunnels and galleries it has etched out in limestone, coral or molluscan shells. The effects of these two species of boring organisms on their hosts have been studied mainly for commercially important molluscs. Hannerz (1956) is the only record of P. ciliata infectingPatella vulgata L, and there is no previous record of anyCliona spp., infections.