16 Marine Shells of the Western Coast of Florida 



with structures definitely comparable to those of the eyes of higher 

 vertebrates. 



Dr. Paul Bartsch, of the U. S. National Museum, claims for 

 the Mollusca first rank in complex organization and intelligence 

 among the invertebrates, and in consideration of the squid and 

 octopus, believes that they surpass some groups of the lower verte- 

 brates. 



The food habits of mollusks are varied. Some gasteropods are 

 predatory and carnivorous, others are vegetarian; some are para- 

 sitic on starfish, sea cucumbers, corals, sponges, and on other mol- 

 lusks; some pierce the egg capsules of their own and other species 

 to prey upon the contained ova and embryos. The food of the pelecy- 

 pods consists of minute plants and animals taken into the diges- 

 tive tract with indrawn currents of water. 



In some groups of mollusks the sexes are separate, in which case 

 the male is usually the smaller. In other groups the mollusks are bi- 

 sexual, and there are some examples of true hermaphroditism. 



Phosphorescence is a property of certain mollusks. The Roman 

 naturalist Pliny remarked this emission of light, and wrote of the 

 Dactylus (pholads), "it is the property of these fish to shine brightly 

 in the dark, when all other lights are removed, and the more mois- 

 ture they have, the brighter is the light they emit. In the mouth 

 even, when they are being eaten, they give forth their light and 

 the same too when in the hands; the very drops, in fact, that fall 

 from them on the ground or on the clothes, are of the same nature. 

 Hence it is beyond a doubt, that it is liquid that possesses this pecu- 

 liar property, which even in a solid body, would be ground for con- 

 siderable surprise".'^ 



There is little definite knowledge of the age attained by mol- 

 lusks. The great size of some gasteropods presupposes many years 

 of life, and the enormous valves of the East Indian Tridacna are 

 the growth of man's three score years and ten, and more. Some of 

 the pelecypods reach reproductive maturity within 12 months, and 

 oysters are known to live for 15 years. 



The phylum Mollusca is divided into five classes: — Amphineura, 

 Pelecypoda, Scaphopoda, Gasteropoda, Cephalopoda. Further sub- 



« Historia Naturalis, Book IX, Chapter 33. 



