ANATOMY AND LIFE HISTORY OP MOLLUSCA. 143 



should be allowed to macerate in a weak solution of acid : two 

 per cent of nitric acid will be sufficient. The time required for 

 the maceration depends upon the condition of the shell. Shells 

 that are not corroded must be selected, and in spite of the numbers 

 of the species on the rocks, uncorroded specimens are not so 

 common as one might expect. For good, clean specimens of adult 

 shells 48 hours maceration I have usually found sufficient. On 

 removal from the pickle the shell can be lightly brushed with a 

 not too hard brush. On examination now the shell will be found 

 to present quite a different aspect. Along each rib will be seen a 

 beautiful series of tubercles for sense-organs, each of the larger 

 eyes occupying the slight ridge made on the rib by the fine concentric 

 lines of growth. There are regular rows also of larger eyes on the 

 depressions between the ribs. Thus the appearance becomes one 

 of much beauty. A series of shining gems radiating in gradually 

 increasing size, studs the surface of the shell, making it quite 

 dazzling. It is very difficult to convey any idea of the effect of 

 the whole without seeming to exaggerate. As far as my experience 

 goes I have seen nothing at all comparable with it, after years 

 spent in the observation of nature. 



Let us now consider a little closely the character of these eyes. 

 Though appearing like a row of shining gems increasing slightly 

 in magnitude from the apex of the shell to the margin, they are 

 not always simple eyes. Sometimes the light will be found to 

 proceed from two eyes of small size placed close together, and 

 sometimes a pair of eyes so closely united that they seem almost 

 like a large oblong one. Sometimes they are a cluster of very 

 minute eyes, as many as five or six, or perhaps more, being found 

 associated together. Though as a rule they occur in rows, this is 

 not without exceptions. Smaller eyes are scattered on the sides 

 of the ribs. I believe they are nearly always smaller when 

 occurring irregularly in this manner. I have chosen this species 

 as a typical one, and as affording with the least trouble an 

 illustration of what I must be excused for calling one of the great 

 wonders of nature. But it must not be supposed that the instance 

 is exceptional • there are many other shells that might have 

 been chosen as examples. 



The question will naturally occur to most persons as to how 

 these structures are known to be eyes, and it would be almost 

 sufficient to answer that they are, in position, in character, and as 

 far as one can judge, in construction, the same organs which have 

 been so intimately examined and figured by Prof. Mosely. In the 

 "Quarterly Journal of Microscopical Science" for January, 1885, 

 there are furnished by the above named Professor, elaborate 

 drawings of such eyes from sections. From these it is plainly 

 seen that there are all the characteristics of an eye, and an ey© in 



