TrachecB from Setiparous Glands. 25 



stigmata are confined io the head, large setse spring from the 

 sides of the segments in the place where stigmata occur in all 

 the Chilopoda and Hexapoda. This curious retention of so 

 many primitive Annelidan characteristics on the part of the 

 Myriapods is after all what one might expect from animals so 

 clearly Annelidan in their rich segmentation. 



(2) The arrangement of the stigmata, hairs, and pigment 

 in the pupa of the vapourer moth {Orgyia antiqua) is very 

 suggestive. The deep black pigment of the skin is relieved 

 at the sides of the abdominal segments by clear white or 

 whitish patclies, running dorso-ventrally and nearly meeting 

 in the ventral middle line. The arrangement is shown in the 

 woodcut. On each side of the stigma is a very definite, more 



post. 



^y ant. 



Lateral view of an abdominal seo;ment of a pupa of a f emaJe 

 Vapourer Moth, showing the " parapodial scars." 



or less circular field covered with long seta3. It is true that 

 the greater part of the dorsal surface is covered with long 

 setai, but no one can examine these setigerous areas under 

 the microscope without being convinced that they are distinct 

 regions. If this arrangement is compared with an Annelidan 

 parapodium, the similarity in the position and arrangement of 

 the setse is very striking. The stigma corresponds to the 

 opening of the acicular gland and the setigerous areas to the 

 setigerous regions of the parapodium on each side of the 

 aciculum. It was especially the aciculum of the dorsal para- 

 podium to which I referred the stigmata of the Hexapoda. 

 We have here, then, traces of a complete dorsal parapodium, 

 as shown in the figure, while beneath it is seen the dorsal 

 part of the ventral parapodium with a similar setigerous area 

 well marked off. More ventrally (not shown in the figure) 

 the white patch is continued, but without setge, almost to the 

 median line. It is the ventral parapodium which I have 

 suggested formed the leg of the Hexapoda. 



Why these extraordinary " parapodial scars," as I propose 

 to call them, should suddenly appear on the pupa is a problem 



