18 NASSA. 



round pellet; under this the creature conceals itself. The fry 

 twist and twirl about by means of their ciliated lobes. N. 

 imitabilis is an article of food in Italy. The generic name is 

 that of a narrow-necked wicker basket used for catching fish, 

 and in such a basket, lobster pots, etc., the Nassa itself is 

 frequently caught, attracted thither by odors savory. 



Naxsa, reticulata is said to be very destructive in the oyster 

 pares of Arcachon (S. of France). It is so numerous that a 

 single tide has yielded 14,600 specimens within a space of 40 

 French hectares (= about 100 acres). The adult Nassa will 

 bore through the shell of an oyster three years old, within eight 

 hours ; but the young shells are far more destructive because 

 they select the tender shells of the very young oysters, some- 

 times piercing fifteen or twenty in succession before their 

 hunger is satisfied. An oyster a month old is destroyed in a 

 half hour.* 



One of the best students of the genus JVas.sa is undoubtedly 

 Mr. F. P. Marrat, of the Liverpool Museum, f Imbued with 

 extreme development views he has, unfortunately, adopted the 

 principle in his scientific work that, the variations of species 

 being illimitable species in fact, as usually defined, being non- 

 existant, the naturalist may apply a specific name for each 

 modification of form, sculpture or coloration ; a principle the 

 absurdity of which must be apparent when it is considered that, 

 no two shells being exactly alike, it will admit of the description 

 of every individual specimen as a " new form/' Mr. Marrat has, 

 however, fully demonstrated the insufficiency of distinctions 

 based on sculpture in a number of species of the genus ; a result 

 most confusing to the systematic, and which leaves the validity 

 of many forms described from single or few specimens very 

 questionable. I am tempted to make some extracts from Mr. 

 Marrat 's latest paper,J the subject of variation being sufficiently 

 important in a general sense to justify me in devoting a few 

 lines to its illustration in this particular genus. 



* Soubeiran, Bull. Soc. d'Acclimatation, 2 Ser., iii, 3, 1860. 



f "On the variation of sculpture exhibited in the shells of the genus 

 Nassa." " On forty proposed new forms in the genus Nassa," etc. 



J " On the Varieties of the Shells belonging 1 to the genus Nassa." 



