182 Greening and Weather Influences. 



Portuguese 0. angulata are bisexual, i.e., male and female 

 separate; whereas our natives (0. edulis) and deep-sea 

 oysters (var. hippopus) are unisexual (=hermaphrodite). 



Qaery has this any relation to the difference in their 

 habitual positions ? 



Greening. With regard to Green Oysters a good deal has 

 been written, but we cannot do better than refer to Professors 

 Herdman and Boyce's interesting compendium of the subject 

 up to date, and their own researches, chemical and physio- 

 logical, with deductions therefrom.* There is also a good 

 repertory on Greenbearded Oysters given by Dr. Bulstrode in 

 the Local Government Board Report.! The Roach River, as 

 many are aware, is the most noted locality for the greening 

 of oysters in our Fisheries District. Still, there is another 

 place less known, Holehaven Creek, where Portuguese and 

 East Rivers have greened remarkably the last two seasons, of 

 which more hereafter (Chap. VI. Oyster Dredging). 



Weather influences. Oysters laid in our shallow waters, 

 creeks and flats are very sensitive to wind and weather. In 

 dull, cold days, or rains and strong winds, they soon get out of 

 order. Atmospheric changes, doubtless, affect their vitality. 

 Besides, these conditions equally react on their microscopic 

 provender, and, this diminished, the bivalves are impoverished. 

 On the more exposed parts of our coasts, during storms and 

 especially strong easterly winds (such as 1881), with low tides, 

 like results ensue. In the beginning of 1879, and still more so 

 in 1891, fatal frosts occurred ; nearly all stations lost heavily. 

 In 1879 the seconds or inferior class oysters suffered most, 

 particularly on the Kentish side and Colne, but " natives " and 

 their brood held out fairly well.J In the Hadleigh Ray and at 

 Whitstable Bay, February, 1895, the water froze right round 



* Lancashire Sea Fisheries Memoir No. 1. " Oysters and Disease," Lond. 1899, 

 with coloured illustrations. 



t 24th Ann. Report for 1894-5 Suppl., "On Oyster Culture in Relation to Disease," 

 Lond. 1896. 



% Coleman in Land and Water, February, 1879. 



