VARIETIES OF OYSTERS. 167 



cirri of the variety nivea are extremely interesting and 

 beautiful objects. They are of different colours in the 

 same individual white, yellow, and brown and are some- 

 times edged with black or purple. 



Some of them are much longer than others, and each 

 has a white line or streak down the middle. The longest 

 have a few milk-white specks, and their tips are curled 

 like a crosier. A few of these tentacles are three-quarters 

 of an inch long. All are contractile and extremely sensi- 

 tive. The outermost row folds back over the margins of 

 the shell. The edges of the mantle are studded with 

 papillae. 



The ocelli do not correspond in number or position 

 with the ribs of the shell, there being two eyelets for 

 every three ribs. All the specimens (about twenty in 

 number) examined by me on the ist of September, 1862, 

 at Oban, shed from time to time a milky fluid which I 

 found was entirely composed of spermatozoa. These 

 moved actively about in every direction, and spread in the 

 water like a thick mist. The quantity emitted by each 

 individual was very great, and after every discharge the 

 water became more turbid. All these specimens had 

 ovaries of a pale-yellow or cream colour. 



This seemed to me a sufficient proof of the monoecious 

 character of the scallop ; and it showed that the mode of 

 its fecundation is the same as takes place in many plants 

 only substituting spermatozoa for pollen-dust, and the 

 waves for the wind or winged insects. Forty or fifty 

 years ago, when this pretty variety was not easily procur- 

 able, and therefore exceedingly rare, a specimen fetched 

 2. Fifty or more may now be had for the same price. 

 The fry remove from place to place, at least in the earlier 

 stages of growth. 



