NATURAL HISTORY OF THE MUSSEL 47 



hand they are seen to be attached to each other 

 in bundles, and the appearance of the fluid to be 

 only slightly milky, the sperms are not quite 

 ready for shedding. 



When a ripe female is opened and the mantle 

 cut into, the fluid which emerges is orange- 

 coloured. Each egg is circular in outline, when 

 viewed under the microscope, and exhibits an 

 opaque granular encircling membrane. By trans- 

 mitted light, it has a slightly brown or greenish 

 brown tinge. It is so small as to be barely visible 

 to the naked eye. Surrounding the egg is a com- 

 paratively deep, transparent layer or envelope, 

 which appears to facilitate the process of im- 

 pregnation by retaining the sperms which may 

 come in contact with it. It probably also protects 

 the egg to a certain extent, but is present only 

 in the very early condition, about the time of 

 fertilisation. 



In the case of the oyster the eggs are retained 

 in the mantle cavity for a considerable time after 

 fertilisation has taken place in the parent. The 

 eggs are then termed white spat. Oysters being 

 hermaphrodite, however, may perform the functions 

 of one or other sex at different seasons. 



In the case of the mussel this is not so : the 



