1898.] 



MICROSCOPICAL JOURNAL 



53 



Embedding in Celloidin will give good results but not 

 to be compared to the Paraffin method when properly 

 mauipuled, in beauty of detail, as well as mounted con- 

 secutive sections, which are needed in the study of this 

 eye. 



There is a considerable ■ variation in the number of 

 eye% found in this bivalve, for while in some as low as 

 64 have been counted, in others over 100 have been found. 

 Perhaps the average number would be found between 

 84 and 96. The eyes are distributed quite evenly along 



the free surface of the mantle. There is also some dif- 

 ference in the size of the eyes in each individual scallop : 

 those which are placed where they are of the most use 

 in seeing being largest in size, though not more perfect 

 in their component parts. The mantle when touched or 

 irritated contracts taking the eyes with it so that although 

 there are no special muscles of motion attached to the 

 eyes yet by the contraction of the mantle they may 

 change their relative position to the objects which sur- 

 round them. The surface of the eye is everywhere sur- 

 rounded by pigmented epithelial cells except the co 



