BRITISH WEI.L-WORMS. 5 



implanted singly, in four rows for about 70 segments in front, and 

 two ventral rows behind. This fact is peculiarly interesting in 

 its bearing on the specimen from Chelmsford. 



j Significance of the foregoing facts. 



It is important that we should understand the force of the 

 facts which are gleaned by a study of the genus. To begin with 

 the head. When I studied the Essex specimen one of the first 

 things which struck me was the anomaly which presented itself 

 here. Three of the known species of Phreovydes have the prosto- 

 mium or head segment divided into halves by a cross furrow 

 at about the middle of its length : and tlie prostomium is rather 

 elongated. This is a peculiar character, met with elsewhere, 

 however, though not among the true Oligochaeta. The seta? are 

 instructive. Here, it is true, we meet with the utmost possible 

 diversity. Mr. Beddard, who has let few things escape him, 

 remarks that " the commencement of a diversity in the form of 

 the setae is seen in PJtveovyctes, where some of the setae are longer 

 than the others, the dorsal longer than the ventral, or vice versa, 

 or the posterior longer than the anterior." Moreover, while they 

 are usually of the typical Lumbricid pattern, viz., sigmoid or 

 /shaped, and not cleft at the extremity, in one species the 

 shaft is straight, in another they are varied on the girdle seg- 

 ments, and in two cases the dorsal setae are either partially or 

 entirely wanting. These are significant modifications. All 

 departures from the type suggest one or two things, either they 

 imply degeneracy or adaptation and progress. This genus is 

 undoubtedly one of an advanced type in many ways. 



I have shewn that the first name which Hoffmeister applied 

 to the genus was Haplotaxis. Was the name chosen to set forth 

 any genuine peculiarity, or was it merely haphazard ? It was 

 suggestive. It is the rule that aquatic annelids possess a 

 longitudinal muscular layer composed of " flat flakes or lamella 

 imbedded in a granular substance." This layer is absent from 

 Phi'covyctes — a fact which struck me when I examined the Essex 

 worm, and one which I find I have recorded in my drawings 

 made at the time when the worm was first placed in my hands. 

 It was, doubtless, this fact which led Hoffmeister to give the 

 name Haplotaxis to the genus. If we turn to the (juestion of 

 brain structure, we find that in Phvcoiydcs this organ has 

 " the simple, bilobed character that is characteristic of the higher 

 Oligochaeta to which this worm is related." (Beddard, Mono- 



