4 BRITISH \VELL-WORI\IS. 



Beddard prepared his Monograph he remarked that "the number 

 of species of this genus is at least four ; and they are all well 

 characterized." This is a great gain. So clearly defined are 

 the different species that, by means of the setse alone we can 

 determine at once under which head a given specimen should 

 fall, and consequently can with equal ease determine whether or 

 not a worm submitted for examination has been already 

 described. 



The first of the species to be described, if we follow Mr. 

 Beddard's arrangement, was Pkreoryctes menkeanus, Hoffm. The 

 number of segments exceeds five hundred, the setai are in four 

 single rows, and the ventral setae exceed the dorsal in length. 

 Leydig, Vejdovsky, Giard, Timm, and others have written on 

 this species. 



Next in chronological order comes Ph. Jilifonnis, Clap., 

 which is al)ont a ipiarter the length of its predecessor, and has 

 the dorsal setas longer than tlie ventral. The setae, moreover, 

 are shorter and much more hooked. Beddard calls attention to 

 the difference of opinion which has prevailed among authors 

 respecting these two species. He admits their possible identit}', 

 but emphasizes the fact that their length is widely different. 

 Michaelsen seems disposed at present to place all the species 

 under one. Ph. lucnhcaniis was described in 1843, Ph. filiforniis in 

 1862. 



Beddard added a third species in 1888 under the title Ph. 

 smithii. This species comes from New Zealand, is a compara- 

 tively stout worm, has its setae paired — which is the case in no 

 other species — the dorsal setae being longer than the ventral in 

 the hinder segments. " The shaft of the seta; which is implanted 

 in the body wall is curved, not straight as in the other species." 

 It may be added that the worm was collected by Mr. W. W. 

 Smith, " chiefly in fresh pools, where it lives in association with 

 a species of Lininodrilns ; one exarrple was discovered in marshy 

 soil ; so that this species is equally at home in water and in damp 

 soil." 



The remaining species belongs to North America. It was 

 described in i8go by Mr. Forbes and bears the name Ph. 

 emissarius. It is readily distinguishable from the rest by reason 

 of the total disappearance of the dorsal setae from four-fifths of 

 the segments. The worm is six or eight inches in length, is 

 composed of nearly 400 segments, very thin. The setae are 



