41 



the thoracic segments in general and the prothoracic one in par- 

 ticular, to bear a primary character. I think I have shown suffi- 

 ciently in chapter III that this a-priori view does not deserve 

 general acceptance. 



In criticizing the different systems and especially that of Fracker, 

 I have had the opportunity of explaining my opinion on the 

 nomenclature. 



Therefore it will not cause surprise that I begin by first 

 taking the abdominal pattern and that, as neither the use 

 of jiumbers nor of Fracker's Greek letters appeared possible, I 

 have come back to the use of names which at the same time 

 express the place of the seta on the segment. In composing my 

 nomenclature I have tried to keep in agreement as far as possible 

 with the following writers : 



Weismanv (1876), MCller (1886), Scudder (1889), Schroder 

 (1894), Quail (1900), J. F. van IJemmelen (1912). 



In accordance with Dyar and Fracker I think that in the 

 composition of a primitive pattern a verruca (wart), a scolus (spine), 

 a tiibercuhim (elevation which mostly bears one or more setae) and 

 a seta ought to be considered homologous with each other. 



I should like to add to this series of homologous organs a 

 pigmental spot. I think that the seta is the original part, and 

 that the other organs are its secondary modifications, A homo- 

 geneous spreading of the setae, as also their complete absence, 

 must be considered as secondary features. 



The reduced patterns of the anal segments have also arisen in 

 a secondary way, though they often lead to pseudo-primitive 

 conditions. 



In discussing the results I intend to refer again to these facts 

 (chapter IX). 



To be able to shorten the descriptions I have also given cyphers 

 to the patterns as a whole : Type I, la etc. The deviations from 

 this pattern can be easily indicated so that with a few words the 

 place of all the setae can be exactly mentioned. In connection with 

 my remarks in Chapter lY it should be pointed out, that the anal 



