10£ The Pearl Oyster of Ceylon, [no. 5, new series, 



and they appear to be then active in moving and attaching them- 

 selves to new localities. During the day, I have only seen, on one 

 occasion, an Oyster form a new byssus. This nocturnal habit, is 

 doubtless instinctive precaution ; for should Oysters move during 

 the day, they are more likely to become the food of fishes, and 

 other animals which prey upon them. Their movements are in- 

 stinctive, and guided by the sense of touch. Darkness suits them 

 better than daylight, of the difference of which they are very sen- 

 sitive. 



Most of the Oysters in which I have found Pearls, had ex- 

 ternal marks of having been retarded in their lateral growth, and 

 displaced in early life from their fixed position on a bank. I am 

 inclined to believe, that Oysters which have abundance of food, 

 and are not disturbed, remain fixed for the last two or three years 

 of their growth to one spot. These are less likely to have a large 

 proportion of pearl bearing individuals among them. This of course 

 requires more extensive practical observation, either on the beds in 

 the harbour of Trincomalie, or on the Pearl banks of Arripo. 



With reference to the formation of Pearls, I have nothing 

 new to add to the accounts found in the best modern books on the 

 subject ; except that one, which modifies the view taken by Sir E. 

 Home; viz. that Pearls are formed from abortive ova. I believe 

 the ova left behind in the ovaria, are not the nuclei of Pearls, but 

 that the ova which escape through the distended coats of an over- 

 grown ovarium, and are imbedded in the interstices of the mantle, 

 become nuclei of Pearls formed in this situation. I have repeated- 

 ly examined seed, or young pearls, in process of formation; and 

 with a magnifying power of 1*5 inch lens, I was able to see dis- 

 tinctly, the outlines of two and three ova through the first or super- 

 ficial layer of nacre, surrounded by groups of ova. It can be rea- 

 dily understood how an overcharged ovarium will, by some acci- 

 dent, or spontaneous evolution, have its coats ruptured, allowing 

 the ova to escape and become inserted in the contiguous attenuated 

 parts of the mantle. As Pearls are more usually found imbedded 

 in the mantle near the hinge, the most likely place where the ova- 

 rium is liable to rupture, I consider this very conclusive of the 

 new theory I have here proposed. I may also observe, that I 



