347 



particularly in the absence of the pronotal comb and the smaller 

 number of teeth in the elytral comb. In the ontogeny' of this 

 species the sequence of appearance of the dorsal combs therefore 

 is this : (i) nuchal comb, (2) elytral comb, and (3) pronotal 

 comb. We may infer from this fact that the combs appeared 

 in the same order in the phylogeny of the species, a conclusion 

 at which Dr. Speiser also arrived from a comparison of the 

 nymph and imago of Eoctenes spasmœ ( = talpa). 



Does this sequence hold good for all Polyctenidœ , and have 

 those species which in the imago state are devoid of one or 

 more dorsal combs lost these combs, or have they never acquired 

 them ? The ontogeny might possibly throw some light on 

 these questions. A comparison of the few immature indi\'iduals 

 which w'e have with the imagines warrants but few generalisations 

 as to the phylogenetic sequence of the combs, as a brief survey 

 will prove. 



The nymph of Polyctcncs molossus has only a guiar comb, 

 which is smaller than in the imago, the apical margins of the 

 head and pronotum bearing no combs, whereas the imago has 

 a nuchal and pronotal comb. There is no elytral comb in this 

 species. 



In Eoctenes spasuice, of which there is a pregnant female 

 in the collection of the British Museum, the embryo as well 

 as the nymph {i.e. presumably all the larval stages) have a 

 guiar and a nuchal comb, both being in the embryo still as pale 

 as the rest of the body, the imago bearing in addition a pro- 

 notal comb and an elytral one. 



In Eoctenes nycteridis, as we have seen abo\'e, the embryo 

 has guiar and nuchal combs, the nymph in addition an ilytral 

 one, and the imago, besides these, a pronotal comb. 



The American Hesperoctenes are devoid of dorsal combs of 

 blunt spines, the guiar one is present in the imago and all larval 

 stages except the sjxcimens which I believe to ha\'e been collected 

 soon after their birth. In these young Hesperoctenes (text-fig. 10) 

 we observe a most }:)U/,/.ling phenomenon. The guiar comb, which 

 is already so well de\-eloped in the embryos of the Old World 

 Polyctenids (as far as embryos are known of them), is entirely 

 absent from the wry young Hesperoctenes, but a comb exceed- 

 ingly similar to half a guiar comb is present on the lirst antennal 



