24<) CEYLON MARINE BIOLOGICAL REPORTS. 



year might show that the current struck either a Httle north or south of the point in question. This, 

 however, would not in the least affect the main facts of its existence and general direction. 



It is exceedingly unfortunate that in spite of all effects we have been unable to obtain any data 

 regarding the oyster beds near Tuticorin. No systematic survey or inspection appears to be carried on 

 round Southern India, and oysters are merely fished when present. Data concerning historical fisheries 

 there (both recent and otherwise) M'ould enable us to collect important data regarding spatfalls, for 

 the monsoon conditions are recorded yearly, and on the Ceylon banks we have records of times when 

 in all probability exotic spatfalls occurred on our owii area. 



In the investigation of these superficial currents we have relied almost wholly on sets or part 

 set^ of bottles which travelled quickly, or in bulk, as more Ukely to indicate the true nature and direction 

 of the prevailing current and be free from extraneous and disturbing factors. Some bottles appeared 

 to have had an erratic course, whilst others were, as expected, not recovered. However, the mass of 

 the evidence was as given in the preceding pages. 



It is remarkable how the productivities of the paar areas coincide with the evidence afforded by 

 currents. Both the Tuticorin banks and those south of TaUaiviUu Point are remarkably barren. This 

 circumstance one would naturally expect to be the case on areas continually swept by currents at critical 

 periods ; whilst on the area mider lease, not only are they protected and free from sweeping currents, 

 but under certain circumstances they may even be replenished by spat derived from elsewhere. 



Apart from the general trend and sweej) of the oceanic current above named, there are, of course, 

 innumerable minor and local eddies along the coast dependent entirely on the configuration of the land and 

 the direction of the wind. They are in every case purely local , and in no way affect the general results just 

 described. We, therefore, need not deal \rith them here, altliough we are cognizant of their existence. 



^^'e append a Hst of the stations where bottles were hberated during each monsoon, giving 

 percentage returns, stations, &c., together with exjilanatoiy charts (A, B, and C). 



We are strongly of opmion that drift bottles ought to be hberated in numbers every year over 

 the Tuticorin banks during the spatting season. It is only by so doing, and by obtaining information 

 regarding the condition of the Tuticorin beds at the time of liberation, that the question of exotic spat 

 can be definitely settled and our results corroborated and enlarged uj)on. Even if the origin of exotic 

 spat was fuUy and finally elucidated, the control of the elements in Nature producing the results would 

 be beyond the power of man. As Steuart said in 1843 (" An Account of the Pearl Fisheries of Ceylon "), 

 '■ the success of the pearl fisheries in the Gulf of Mannar depends primarily upon natural events beyond 

 the control of man. Nevertheless, we may by the most vigilant attention and good management watch 

 the progressive workings of Nature, and not fish up the oysters before they have reached maturity, nor, 



after they contahi the pearl, suffer them to die on the banks and the pearl to be lost We may 



presume from past experience that unsuccessful intervals mU continue to recur We camiot 



cause the spawn to settle down upon nourishing groimds. These are events beyond the control of man. 

 The wand, the waves, and the uncertain currents of the ocean carry the embryo over unUmited space. 

 It is only when in the infinite wisdom of the Creator of all things the oyster broods descend upon 

 banks suited to nourish and support it that it comes within our hmited power to watch its advancmg 



age and to fish up the respective deijosits in succession " A knowledge of the true facts is, 



however, essential to successful culture, as they enable us to lay and mature our plans accordingly. 



III. — Bottom Ciieeents, 



Our knowledge concerning bottom currents over the plateau is confined entirely to the area under 

 lease. Of the movements which the bottom layers of water may undergo on the ground still under 

 Government control we have no information, and even on the northern area our knowledge is limited 

 to the conditions existing during the north-east monsoon. These, however, give some indication of 

 what the conditions must have been during the preceding south-west monsoon. 



From what has been said in the foregoing pages on the surface drifts prevalent over the plateau 

 under lease, it is evident that no serious disturbance at the bottom could accrue from the conditions 

 existing at the surface. The loss of oysters through a bottom current implies a current sufficiently 

 strong to actually tear oysters from their anchorage. Steuart, writing in 1843 (" Account of the Pearl 



