some voracious fish. This is known as protective adaptation, and was 

 doubtless brought about in the following manner : 



" The murices or their ancestors did not at first have spiny shells, 

 and they fell an easy prey to the fishes. As time went on, a few 

 individuals, through some modification of their environment, developed 

 small spines or prominences. The animals having these were not eaten 

 by fishes, as the knobs and spines caused them pain in swallowing; 

 therefore they preferred the animals with smoother shells. In time, 

 this modification caused a weeding-out process, the animals without 

 spines being exterminated, and those with spiny shells increasing in 

 number and becoming more spiny as one generation succeeded another. 

 This continued until the present time, and is going on even now. 

 Another interesting fact concerning the development of this ornamen- 

 tation is that the smoother shells inhabit rocky shores on which the 

 waves are beating with greater or lesser violence, while the more spiny 

 individuals live in protected and comparatively still waters. This but 

 adds additional weight to the theory of survival by protection, for the 

 fishes which feed upon these shells do not, as a rule, inhabit localities 

 where the water is rough, as along a rocky shore, but live abundantly 

 in protected bays and lagoons in which the spiny murices are found. 



" One of the most beautiful of the rock shells is the Venus comb, 

 found in China, Japan, and the Indian Ocean. It belongs to a group 

 of shells which is characterized by a long canal and long, pointed spines 

 which extend along the edge of the canal like the teeth of a comb, 

 whence the name. The colors are yellowish or whitish, and in one 

 species the spines are tipped with black. Another rock shell which 

 is found on the mantel of almost every household is known as the 

 branched rock shell, Murex ramosus. This mollusk is found in the 

 Red Sea, the Indian Ocean, New Zealand, Australia, and the Central 

 Pacific Ocean. It attains a large size, some specimens reaching the 

 length of a foot and weighing several pounds. The aperture is fre- 

 quently tinged with a deep, beautiful pink. In many households the 

 large shells of this species are used as flower -pots, suspended over 

 the window by chains, and for this purpose they are certainly very 

 ornamental. 



" The apple rock shell, Murex pomum, is of home production, being 

 found on the shores of Florida and throughout the West Indies. It is 

 not as attractive as the shell I have just mentioned, but is very com- 

 mon, every collector having several specimens in his cabinet. The 

 horned rock shell, Murex axicornix, and the burnt rock shell, Murex 

 adustus, are interesting members of this family. The latter name, 



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