June T, 1907] 



SCIENCE 



899 



suggested that detailed investigation of the 

 Coastal Plain may favor the hypothesis of a 

 northward extension from the south. Such a 

 possibility may be favored by a route across 

 the Appalachians which seems to have been 

 very generally overlooked as a highway — the 

 Kanawha Eiver Eoute — which reaches south 

 into North Carolina. This is a stream with 

 a remarkable history whose biological signifi- 

 cance is worthy of detailed investigation, not 

 only from the standpoint of aquatic inverte- 

 brates, but also of higher groups as well. 

 (This is perhaps particularly true of birds.) 

 In view of the antiquity of this route it seems 

 very improbable that animals should ignore it. 



In considering the crawfish characteristic of 

 the natural physiographic regions of the state 

 certain interesting correlations are evident. 

 The Coastal Plain possesses two species, diog- 

 enes and Umosus; the Piedmont Plateau and 

 Great Allegheny Valley, which form a unit, 

 are characterized by Umosus and hartoni; the 

 Allegheny Mountains by hartoni, with an in- 

 vasion along the Susquehanna by Umosus and 

 an isolated colony of ohscurus — ^both are due, 

 Ortmann thinks, to the influence of man. A 

 map of the state showing the location of past 

 and present canals would greatly aid one in. 

 understanding the extent of this influence. 

 The Allegheny Plateau, on account of its 

 proximity and drainage into the great interior 

 glacial preserve, has the most varied crawfish 

 fauna — six species: propinquus, ohscurus, 

 caroUnensis, monongalensis, diogenes and 

 hartoni. It is thus seen that most of the 

 species have invaded the state from the west- 

 ward and that there is a marked attenuation 

 of the fauna to the eastward. 



The life histories of the species are consid- 

 ered in detail, the seasonal life history may be 

 outlined as foUows; a fall mating, a spring 

 spawning season, an early summer season when 

 the males are in the first form. The species 

 which follow this cycle include, provision- 

 ally, ohscurus, propinquus and var. saniorni, 

 Umosus and diogenes. These forms comprise 

 what Ortmann calls the * warm water ' type 

 and have a restricted breeding season. A sec- 

 ond class includes those species which breed 

 and spawn practically the year around, the 



' cool water ' type, and includes hartoni, mon- 

 ongalensis and probably caroUnensis. 



In ohscurus, eggs are laid in April, hatch in 

 May or June, and by September or October 

 the crawfish are 40 to 55 mm. long, and the 

 males are in the first form, the females are 

 mature and copulation takes place from Sep- 

 tember to November. The winter is passed 

 without change, and in April the females 

 spawn and in June moult, the males having 

 moulted in May. The fall moult ranges from 

 August to October, and a second breeding 

 season follows, and in the following year a 

 third, after which they survive the winter, the 

 males dying perhaps in early spring, and the 

 females in June. They may thus reach the 

 age of three years. 



On account of the almost continuous breed- 

 ing season of the ' cool water ' species it is 

 difficult to recognize broods and thus deter- 

 mine the detailed life history. 



At present the known economic relations of 

 crawfish are rather limited. They are used as 

 food to a limited degree, especially about 

 cities, but are very generally used as bait, 

 hence the confusion which fishermen are likely 

 to introduce into the problem of the original 

 range of species. As scavengers they may be 

 very beneficial, and occasionally dams may be 

 injured, but these subjects have received but 

 little attention by the public or naturalists. 

 Their enemies include a wide range of ani- 

 mals, especially among the vertebrates. 



The final section of Ortmann's paper is de- 

 voted to a discussion of the relation which this 

 study of Pennsylvania species bears to the 

 problems of evolution; mutation and isolation 

 in particular. Ortmann criticizes de Vries's 

 statement that species are formed only by 

 mutation. He then considers in detail the 

 evidence for marked variation or muta- 

 tion among the Pennsylvania species and 

 concludes that the differences between them 

 are very constant and the variations slight, 

 adding that " Anything that looks like a ' mu- 

 tation' in de Vries's sense is entirely un- 

 known." Even the differences between well- 

 defined species " are so slight that they can 

 not be regarded as representing ' mutations,' 

 that is to say, sudden leaps in a progressive 



