238 G. W. HART ON OYSTERS AND OYSTER-SPAT. 



the other hand, if it be necessary to saturate the water at some 

 early date with spermatozoa for the general impregnation of the 

 bulk of oysters, it is certain that to reduce the number beyond a 

 certain degree, and so remove the individuals to a greater distance 

 from each other, is destructive to the fertility of a bank, as the 

 chances of the oyster becoming fecundated by the spermatozoa of 

 another is reduced to a very low point. 



The young oysterling having been ejected by its parent in a per- 

 fect state — in favourable seasons at once attaches itself by its pad to 

 the first object it meets with ; if it be an unsuitable one — mud — it 

 perishes. If suitable a growth of shell immediately takes place, 

 and it is this layer of shell matter that forms the attaching medium. 

 There is no requirement for a special organ for the purpose of 

 attachment, and therefore none exists — and when one layer of shell 

 has been made another follows it, and so on continually, with small 

 periods of rest. So that the point of attachment, which was at the 

 first in front, becomes in a short time left in the rear, and it is this 

 which has led to the notion that the oysterling is attached in the 

 first instance by the heel of the shell. 



Mr. B. T. Lowne regarded the question of self-impregnation as 

 one of very great importance ; he said he could see no reason why 

 oysters should not be self-fertilizers under some circumstances, 

 although under others a cross between two individuals might take 

 place ; when the spermatozoa of an oyster are discharged into the 

 water it is almost inconceivable that they should not fecundate the 

 ova of that oyster, unless some provision of a mechanical kind 

 existed to prevent it, and it is difficult to understand what that 

 provision could be which would not equally, or almost equally, 

 render fertilization from another individual difficult or uncertain. 

 We know that in plants, which are almost all hermophrodites, self- 

 impregnation is the rule, and yet a great variety of means are pro- 

 vided for effecting a cross between two individuals. Whilst from 

 the valuable researches of Mr. Charles Darwin it appears that 

 even should the pollen of another individual come in contact with 

 a stigma which has already been sprinkled with pollen from 

 anthers in the same flower, even though the pollen tubes had 



