ORIGIN AND SIGNIFICANCE OF SPINES 55 



of the general armor. In Stegosaurus 46 the efficient offen- 

 sive and defensive weapons were the huge spines on the tail, 

 and it is interesting to note, as a parallel to this condition, 

 that the greatest nerve centres were in the sacrum, and 

 therefore posterior also. 



No group of vertebrates shows such a variety of protective 

 and offensive characters as the fishes. Many of the older 

 types were heavily plated, while in others the fin spines were 

 greatly developed. Among modern forms the protective 

 character of the spines is well shown in types like the Spiny 

 Box-fish Chilomycterus geometricus and Diodon maculatus. 

 A combination of mechanical and optical protection is afforded 

 in the remarkable Australian Pipe-fish Phyllopteryx eques 2 ' 

 (figure 49). This fish has numerous spines and ribbon-like 

 branching filaments, the former giving it a mechanical defence, 

 and the latter assisting in its concealment among sea-weeds, 

 to which it bears a striking resemblance. 



Spines for protection are extremely common among insects, 

 even in larval forms. They have been so frequently noted as 

 to require no elaboration here. Packard 54 has ably discussed 

 the origin of nodes, tubercles, and spines among certain 

 caterpillars. Among the forms which feed exclusively at 

 or near the ground, he finds the body usually smooth, while 

 those feeding on trees or on both trees and ground are 

 often variously spined and tuberculated. These ornamental 

 features arise from the modification of the piliferous warts 

 common to all lepidopterous larvae, and he concludes that the 

 trees were more favorable for temperature, food, etc., than 

 the ground, and that an increase of nutrition and growth 

 force led to the hypertrophy of these warts into tubercles and 

 spines. Having thus arisen, they immediately became useful 

 for protection from birds and parasitic insects. 



Among the Crustacea there are also numerous examples 

 of protective spines. These may be confined to parts of the 

 body and legs especially exposed, or the entire animal may 

 partake of the spiny character, as in the crab Echidnoce- 

 ras setimanus, where even the eye-stalks and antennae are 



