122 THE SCOTTISH NATURALIST 



The observations are based on notes made upon the 

 behaviour in an aquarium of about sixty examples, and 

 are detailed under the following headings: (i) Animal 

 matter as food ; (2) vegetable matter as food ; (3) inorganic 

 matter as food ; (4) the search for food ; (5) the positions 

 and postures adopted in feeding ; and (6) the time spent 

 in feeding. In the first section it is surprising to find how 

 varied is the diet of these lowly creatures. Several species 

 of fish serve as victims, but usually only the softer parts are 

 devoured, although an exception to this rule is recorded. 

 Various species of crabs and smaller crustaceans are 

 attacked, and even their exoskeleton and faeces eaten, as 

 are also the soft parts and even shells of molluscs. Other 

 echinoderms, polyzoa, and worms, also coelenterates and 

 sponges, form part of the menu, and even sand, gravel, and 

 chalk. A number of objects eaten by the Urchins are 

 illustrated in a figure, which shows clearly the amount 

 gnawed away by their teeth. It is pointed out, however, 

 that seaweed constitutes by far the greater portion of the 

 food of these animals, and this accords with our previous 

 ideas on the subject. The section on the " search for food " 

 shows how slowly yet surely the Urchins discover the 

 presence of a meal, even though the desired object be 

 placed from one to two feet away from the animal. 

 Whether the Urchin possesses a sense of smell and dis- 

 covers the tit-bit by this faculty is not stated, but it is 

 interesting to note that " the first sign given by a Sea- 

 Urchin that it has detected food is the extension and eager 

 waving in the water of those tube-feet which are on the area 

 of the animal nearest to the food." The time spent in feed- 

 ing is curiously long — four large individuals remained in a 

 mass of seaweed for a fortnight, in the course of this period 

 reducing the heap entirely to faecal pellets. Three other 

 examples remained fixed to a dead Hermit Crab for three 

 whole days ; while one Urchin, with a predilection for common 

 blackboard chalk, appeared to be occupied with this peculiar 

 diet for nineteen hours. 



