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legs (pedes spurii). Some of them, in imitation of Kowalewsky 

 (1871) and Tichomieoff (1879) seek to provide all the abdo- 

 minal segments with them. This conception is supported by em- 

 bryology and comparative morphology. On the other hand 

 Deegener (1909, p, 3) considers these pedes spurii to be „secon- 

 dary, adaptive, provisorial organs". With a view to this contro- 

 versy it is worth while to point out how, as early as 1886, Muller 

 called attention to the primary seta N°. 6, which occurs on the 

 legless segments, but which is absent on the segments 6, 7, 

 8 and 9 (= abdominal 3, 4, 5 and 6). 



Fracker who has a different conception of these setae, does 

 not go into this question at all. We see therefore that there are 

 many different opinions on the number of the abdominal segments 

 and on the question whether the abdominal legs are primitive or 

 not. I think that I have adduced some proofs in Chapter VI of 

 the presence of more than ten abdominal segments, and I believe 

 that the regular presence of the seta pedalis also on those segments 

 which bear no legs, should be taken as a proof that originally 

 all the abdominal segments were provided with legs. This con- 

 ception is also supported by embryology. 



CHAPTER y. 



Nomenclature and primitive pattern. 



With a view to making the descriptions as clear as possible 

 it is desirable to introducé a well defined nomenclature. 

 Weismann (in 1876) made a first attempt, but as I pointed out in 

 chapter II, he considered the setae of no importance and only 

 gave names to the stripes. 



ScHRÖDER also confined himself to these in his study on the 

 Geometridae (1894). He found the same stripes as Weismann on 

 the Sph'mgidae but in larger number. For the intermediate stripes, 

 he introduced particular namos which, however, can be brought 

 back to Weismann's nomenclature. 



