192 Prof. Asa Gray on the Question 
8. Lithobius Saussuret, n. sp. 
Lamina cephalica obcordata, fere eque longa ac lata, lateribus 
semicirculariter rotundatis, levis, pilis sparsis vestita. An- 
tenne sat longe, corporis dimidiam longitudinem haud asse- 
quentes, articulis 27 parce setosis, ultimo penultimum lon- 
gitudine haud multo superante, composite. Oculi 
Coxe pedum maxillarium secundi paris dentibus 5+5 
nigerrimis, brevibus, validis armatz, sinu mediano subpro- 
fundo. Scuta dorsualia anteriora levius, posteriora mani- 
festius rugulosa, at non granulata,subglabra, 9X, 11%, 13u™ 
angulis productis, 7" margine postico medio profundesinuato. 
Port coxales 5,6, 7,6 magni, subrotundi. Pedes primi paris 
calearibus 2,3,2. Pedum analium articulus primus calcari 
singulo, laterali armatus. Pedes anales breves, sat inflati, 
unguibus binis, calearibus 1,3,3,1 armati. Unguis geni- 
talium femineorum obsolete trilobus, lobo mediano laterales 
haud multo superante; calcarium duo paria. Color casta- 
neus vel brunneus. 
Longitudo corporis 23 millim., antennarum 9 millim., pedum 
analium 6-7 millim. 
Hab. in Mexico circa urbem Orizaba (H. de Saussure). Unum 
tantum specimen ( @ ) vidimus. 
Upsala, February 10, 1875. 
XXV.—Do Varieties wear out, or tend to wear out? 
By Professor ASA GRAY *. 
THIS question has been argued from time to time for more 
than half a century, and is far from being settled yet. Indeed 
it is not to be settled either way so easily as is sometimes 
thought. The result of a prolonged and rather lively discus- 
sion of the topic about forty years ago in England, in which 
Lindley bore a leading part on the negative side, was, if we 
rightly remember, that the nays had the best of the argument. 
The deniers could fairly well explain away the facts adduced by 
the other side, and evade the force of the reasons then assigned 
to prove that varieties were bound to die out in the course of 
time. But if the case were fully reargued now, it is by no 
means certain that the nays would win it. The most they 
could expect would be the Scotch verdict, ‘ not proven,”’—and 
this not because much, if any, additional evidence of the actual 
wearing out of any variety has turned up since, but because a 
* From Silliman’s ‘ American Journal,’ February 1875. 
