468 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.46. 



The occurrence of the white variety in a cave indicates that the ordinary form is 

 probably to be met with west of the Rocky Mountain range. 



Had I not had a series from the Carter Caves connecting the white variety with the 

 ordinary out-of-door plumbeous form, I might have been inclined to regard it as a new 

 and undescribed species, although it represents no structural differences in the form 

 or length of the appendages from the normal form. But the series affords a capital 

 example of the successive steps in the formation of a new form, whether we call it a 

 new variety or species, while the causes of the changes are sufficiently apparent. 

 Examples such as these and others I have before me to be hereafter described amount 

 almost to demonstrative e-vidence of the truth of the doctrine of the transformation of 

 species. 



Some years later Packard ('88, p. 65) described from caves in Ken- 

 tucky and Virginia a form that lie took to be the same white variety, 

 but for which he used, perhaps inadvertently, a second name — 

 pdUidus. His account follows : 



Tomoceribs plumbeus Templeton, var. pallidum. — One specimen from Zwingle's Cave 

 was but slightly changed, being almost wholly plumbeous; it occurred one-quarter 

 of a mile from daylight (Sanborn). 



In a number of other specimens from Zwingle's Cave and others of the Carter Caves 

 the body is white, as well as the spring and the legs, but the tarsi retain a slight plum- 

 beous tinge. The antennae are partly pale, the two basal joints being bathed with 

 leaden gray. Ten examples collected by us had distinct black eyes, but minute and 

 angular in outline, having suffered a considerable reduction in size. Specimens col- 

 lected by us from the ice-house cave were white, with dusky antennae and black eyes, 

 and were like those just described. 



Specimens from X Cave were all bleached, like thoBe from the other Carter Caves, 

 but in some examples the eyes were connected by a narrow, black band. 



Specimens from Weyer's Cave and the adjoining Cave of Fountains were just like 

 those in the Carter Caves, being white, with small, black eyes and dull, purple leaden 

 antennae and tarsi. Those in the New Market Cave were white, with black eyes and 

 dark lead colored antennae. 



In One Hundred Dome Cave specimens said to have been collected one-quarter of a 

 mile from the entrance were all dark, of the usual out-of door plumbeous color. 



Remarks. — It is e"\ddent that the var. pallidus has been produced by the influence 

 of its cave life. Var. pallidus occurs in a cave near Salt Lake, Utah, and the specimens 

 do not differ from the bleached ones in the Kentucky and Virginia caves. The tnmk 

 becomes bleached, while the extremities of the antennae and legs retain somewhat of 

 the colors of the out-of-door form. None have been found without eyes. The shal- 

 lowest caves, such as the ice-house cave, in Carter County, Kentucky, as well as the 

 deeper ones, possess this variety. We also find the normal plumbeus in similar caves, 

 though probably near daylight, but the inference that the pale bleached variety has 

 been produced by want of light is a natural and the only possible one. It is proved 

 by finding in Zwingle's Cave a slightly changed plumbeus associated with numerous 

 pallidum. 



Packard's types of his cave CoUembola seem to be lost. They were 

 not in the Museum of Comparative Zoology, Cambridge, Massachu- 

 setts, with the rest of his material when I searched for them about 

 fifteen years ago, and Packard wrote to me that he did not know 

 where they were. I have made efforts to obtain specimens of this 

 form from collectors of cavernicolous species, but without success 

 as yet. 



