P0LYCH2ETA—BENHAM. 
49 
dorsum and may even interdigitate with those of the opposite side (pi. XXVII, fig. 3). 
He says further (p. 444) that although they are not present in all individuals, he has 
found them in both small and large specimens, and he suggests that their presence may 
bear some relation to sexual maturity. I have examined several parapods taken from 
both large and small specimens with the especial object of finding these fine capillary 
bristles. Occasionally some of the chsetse may be seen edgewise and so appear thinner 
than when seen on the flat surface, and frills are then seen to project from both edges 
giving an appearance somewhat like Ehlers’s figure. But I do not find such difference 
in length as he found. Gravier does not mention their occurrence in his specimens, 
and on the presumption that we are dealing with the same species, this is the only 
feature in which ours really differ from those examined by Ehlers. I may add that 
McIntosh does not mention such bristles in his account of L. crosetensis. 
So far, then, as the present specimens are concerned, all the dorsal chsetoe are 
alike in structure, though they differ in length ; those in the lower part of the bundle 
being about half the length of those in the upper part. 
The same difference in size exists amongst the ventral chsetse. The ventral 
chaetse (figs. 46, 47) which in L. crosetensis , McIntosh states are “ not furnished with 
long spines, and have a distinct sub-apical tooth;” have in the present case, as Gravier 
has figured (pi. IV, fig. 49) certain pronounced spines or teeth amongst the upper frills, 
which are absent in the lower frills. In some chaetse two such spines occur on one side 
and one on the other; in other cases, two on each side. The frilled region is long, 
consisting of about 20 frills which are discontinuous in the distal region, but become 
continuous over the greater part. Ehlers says little about the ventral chaetae, except 
to state that the apex is simple. Why then should he refer it to the species L. crose¬ 
tensis ? 
However, in Hermadion rouchi, although most of the ventrals have a simple apex, 
with no sign of a sub-apical tooth, there is occasionally a sub-apical “ step,” which seems 
to indicate a tooth that has been worn away. And Gravier states that in some of his 
specimens he found a tooth. 
More than one zoologist has in recent years commented upon the difficulty of 
distinguishing between the two genera, Lagisca Malmgren and Hermadion Kinberg, as 
well as upon the question of the distinction between them and the genus Harmothoe 
Kinberg. Most writers accept the last genus in an extended sense as including several 
of Malmgren’s sub-genera, though Professor McIntosh still retains most of the latter; 
and in his splendid monograph of the British Annelids, published by the Ray Society, 
these names are even used as generic. 
I need not discuss this matter further as Baron de St. Joseph (1888, p. 150) has 
given the history of these names. It was Willey (1902), I believe, who first drew 
attention to the resemblance between Lagisca and Hermadion . And Fauvel (1916) 
has recently summarised the main points in the controversy raised by him and also 
discussed by Gravier (1911). Fauvel concludes (p. 426) that Hermadion is distinguish- 
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