C. E. Beecher — Origin and Significance of Spines. 263 



45 



is 



them (Chamceleon Oweni) is here shown (figures 45, 46). The 

 male has three horns, one on the snout and two on the fore- 

 head. They are supported by bony excrescences from the 

 skull. From the peaceable nature of these animals, Darwin 

 concludes that " we are driven to infer that these almost mon- 

 strous deviations of structure serve as masculine ornaments." 



The males of the tropical American 

 genus of fishes, Callichthys, " have the 

 spines on the pectoral fins stronger and 

 longer than those of the female, the 

 spine increasing in size as the male 

 reaches maturity " (Seeley 65 ). 



Among insects, the males of many 

 beetles belonging to the Lamellicorns 

 have long horns arising from various 

 parts of the head and thorax. One of 

 the best known forms is the Hercules 

 beetle (Dynastes nereides). Bateson 5 

 states that, in this and other genera, it 

 is commonly found that the males are 

 not all alike, but some are of about the 

 size of the females and have little or 

 no development of horns, while others 

 are more than twice the size of the 

 females and have enormous horns. 



These two forms of male are called " low " and " high " males, 

 respectively. Among the males, similar dimorphism in respect 

 to size and length of horns occurs in Xylotrwpes gideon, and 

 in the stag beetle (Lucanus cervus, L. titanus, L. damd). 



In many of these cases, the horns are evidently protective 

 and not developed through the selective influences of the 

 female. In such cases, the habits of the male are supposedly 

 different from those of the female. Thus, Wallace 70 suggests 

 that the horned males of the coleopterid families Copridae and 

 Dynastidse fly about more, as is commonly the case with male 

 insects, and that the horns are an efficient protection against 

 insectivorous birds. These interpretations clearly do not come 

 under the definition of sexual selection as restricted to the 

 choice of either sex. Beauty, voice, or strength, may influ- 

 ence the selection of a mate by the opposite sex, but when the 

 habits of the sexes are different and certain characters arise in 

 response to this change, the explanation is then really found in 

 the law of adaptation or physical selection. 



V. Secondarily from mimetic influences. (A 5 , B 4 .) 

 Natural selection may aid in furthering and preserving a 

 spinose organism after the spines have originated through any 

 primary cause. One aspect of this influence may be treated 



Figure 45. Profile of 

 head of Chamaeleon Oioeni; 

 male. \. 



Figure 46. Female of 

 the same species. -£. (After 

 Darwin.) 



