POLYCH^TA. — BENHAM. 217 



area of maximum development is more extensive, reaching 

 to the seventieth. It may be noted that both these individuals 

 ai"e " spotted " with red, and are from the same locality ; 

 but No. 12 occurs with another more normal in colouration, 

 and normal so far as the gills are concerned (No. 6). The 

 maximum number of filaments in the fore body is usually 

 five or six, but in one, otherwise normal (No. 3), it rises to 

 seven, and even here and there to nine, while in another 

 instance (No. 4) it is ten or occasionally eleven. On the other 

 hand, in No. 5 the number of filaments is as low as two. 



In all but one s2:)ecimen, and that one of the " abnormals," 

 the number of filaments decreases slowly and fairly regularly 

 towards the hinder end, and the gill is continued to the 

 extremity or is only absent on the last half-dozen segments, 

 which are, of coxuvse, very small. In the abnormal individual 

 (No. 11) the gill after decreasing, increases near the hinder 

 end to seven filaments, and further back to eight before 

 undergoing the usual terminal decrease. 



The two " abnormals " differ then not only in the colour- 

 ation but also in some matters concerning the gill ; yet an 

 examination of one of them (No. 12) the jaws are precisely 

 like that which I studied in detail (No. 1), and in all other 

 respects these two agree with the rest. It appears to be 

 merely a local variation. 



The form of the gill in all these twelve is very uniform : 

 the filaments broad, closely set, nearly or quite touching one 

 another, or in some case overlapping. When fully developed 

 the lower filaments are longer than the dorsal cirrus ; one 

 or more of them may bifurcate ; not infrequently the axis 

 projects but slightly beyond the uppermost filament, as if 

 it were capable of budding oft' additional filaments at this 

 point. In one individual the gill is much smaller than usual 

 (No. 10) and the filaments more delicate and further apart. 



Other variations, such as length, depend on the state of 

 preservation. The colour in some is copper. The white 

 " collar,"' too, is remarkably sporadic ; it might at first sight 

 seem rather a characteristic feature, but such a '" collar " 

 appears as a variation in other species such as E. aphroditois. 

 MTntosh notes that in his specimens a " collar " exists on 

 segment II in those from Twofold Bay, while it is absent 

 in the Bass Strait specimens. 



The segment in which the acicular chseta first occurs is 

 also subject to variation, though usually somewhere about 

 the thirtieth, it may occur either before or after that segment. 

 These variations are tabulated below. 



