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Eoctenes the guiar comb. This assumptiun means that Hcs- 

 peroctenes branched oft" when there was as yet neither a guiar 

 nor an antennal comb. Another possibility is that the antennal 

 comb of the young Hesperoctenes is the phylogenetically oldest 

 one in the whole family, and was transferred in the next phyletic 

 stage to the head and replaced on the antenna by small spines 

 directed outward. In this case we must consider Hesperoctenes 

 as having preserved an ancestral stage which has been dropped 

 by Polyctenes and Eoctenes. Whichever alternative we may 

 favour, Hesperoctenes appears in either case as an ancient branch 

 of the family. The symmetry of the tarsal claws and the more 

 normally developed anterior tarsus in Hesperoctenes are further 

 evidence that this American genus is more ancestral than the 

 Old World genera of Polyctenidœ. Does the absence of dorsal 

 combs in Hesperoctenes point in the same direction ? The 

 spines of the combs are modified bristles. Their place is taken 

 by bristles in the immature stages if a comb is restricted to the 

 adult, and the same is the case in the adult Polyctenids if a 

 comb is absent in the respective species. In Adroctenes we 

 meet with all intergradations between a pointed bristle and a 

 blunt spine. In the metamorphosis of the Polyctenids we 

 only observe an increase in the number of combs and number 

 of spines in the combs, nowhere a decrease, apart from the 

 comb on the first antennal segment of the young Hesperoctenes. 

 This may be taken as evidence that also in the phylogeny of 

 the family an increase in the combs took place. On the other 

 hand, we have no evidence of any kind for a decrease in the 

 number and size of the dorsal combs. It is therefore highly 

 probable that the species with three dorsal combs are (in this 

 respect) younger than the species with two or no dorsal combs, 

 Hesperoctenes, without such combs, but with a nuchal row of 

 bristles, being the most ancestral. No adult Polyctenid is 

 as yet known which bears only one dorsal comb of blunt spines. 

 If such a species exists, it will presumably be the nuchal comb 

 which is present. 



