92 STUDIES IN EVOLUTION 



with a solid deposit of lime. Similar examples could be 

 multiplied indefinitely. Since, however, but few of them 

 are spiniferous, their consideration does not properly come 

 within the scope of the present discussion, though, as is 

 well known, some of the attenuate forms often enlarge and 

 contract periodically, such enlargements frequently leaving 

 prominent laminae or nodes that are sometimes differentiated 

 into spines. They suggest the observations on growth, senes- 

 cence, and rejuvenation, made by Minot,^^ who showed that 

 in guinea pigs from a very early age the increments of 

 growth are in a steadily decreasing ratio to the increase 

 of weight of the animal. This led to the general conclusion 

 that the whole life of an individual is a process of senescence 

 or growing old. 



Spines arising by a real pathologic or diseased condition 

 of the individual can have little or no effect in producing a 

 normal spiniferous variety or species. However, some note 

 should be taken of them, especially as they may be con- 

 genital, and thus appear through several generations. In the 

 human species the peculiar skin disease known as ichthyosis 

 sometimes produces spiniform excrescences, and the victims 

 are commonly called "porcupine-men." The most cele- 

 brated instance was the Lambert family. HaeckeP' gives 

 the following account of this family: "Edward Lambert, 

 born in 1707, was remarkable for a most unusual and mon- 

 strous formation of the skin. His whole body was covered 

 with a horny substance, about an inch thick, which rose in 

 the form of numerous thorn-shaped and scale-like processes, 

 more than an inch long. This monstrous foj'mation of the 

 outer skin, or epidermis, was transmitted by Lambert to his 

 sons and grandsons, but not to his granddaughters. The 

 transmission in this instance remained in the male line, as 

 is often the case." Other similar examples are cited by 

 Gould and Pyle,2i and the disease is described as "a morbid 

 development of the papillae and thickening of the epidermic 

 lamellae." 



