160 ANATOMY AND LIFE HISTORY OF MOLLUSOA. 



optical peculiarities that are seen in the previous two species. The 

 eyes are of much larger size and not so deeply set as in the last 

 case. They give the shell a very beautiful appearance because of 

 the multitudes of them which beset the surface ; but still there is 

 no approach to the symmetrical arrangement which I have seen 

 in the case of Patella. On making my first examination of 

 Siphonaria I did not find the eyes, and was almost giving up the 

 search when a fresh shell showed me the multitude and size of the 

 organs. In proportion as the shell is dry and withered, so is it 

 difficult to see them, and in those which have been kept in spirits 

 for any length of time it is nearly impossible. 



At present so much is required to complete observations that I 

 am reluctant to give any list of other species in which it seems to 

 me that I have observed shell-eyes. If the organs be such as I 

 imagine them, then I may say that there are many shells I have 

 examined on which some such have been observed ; though 

 the number may be very small in some species, especially those 

 with a compact outer plate and 'high colouring, and porcellanous 

 shells. Still the proportionate number of shells I have carefully 

 inspected is small. The difficulty of dealing with them can be easily 

 understood when it is remembered how often shells are overgrown 

 by a thick matted periostraca in which algse are extensively 

 entangled, and all sorts of foreign organisms growing. To remove 

 this must, in nine cases out of ten, destroy all traces of eyes. 

 Persons are greatly mistaken who think that the brilliant tropical 

 shells, the cones and the cowries which adorn most houses, are 

 found upon the coral reefs in the way in which they beautify the 

 sideboards and the mantelpieces. In their living state they are 

 anything but attractive objects, and are, without exception, 

 disguised in a thick greenish and slimy coat which requires much 

 care, patience and labour to remove. Much of this belongs to the 

 living tissue, and it has never been taken into account by collectors. 



The naturalists in the early stages of that portion of zoology 

 which occupied itself with the Mollusca, took no heed of anything 

 except the shell. But even when more reasonable and sensible 

 systems had been followed, the outside of the shell and its clothing 

 received no attention, and it is not known except in a very few 

 cases. I well remember the effect upon my own mind, when 

 landing for the first time upon the great Australian Barrier Reef, 

 which may be called an emporium for the glories of the deep, or 

 the spoils of the ocean, especially in shells. I began to look about 

 for one of the most beautiful of these treasures, which, to my 

 mind can vie with even the Conus gloria-mar is. I mean Conus 

 marmoreus with its intense blackish-brown hue, thickly studded 

 with broad, tongue-shaped white marks. Having been informed 

 that it was common, I expected to see it easily, since its colouring 



