bearing on the origin of Insects. 159 



In an inland species with short antenna (apparently 

 Mncliilis [Forhicina) polypoda) which I have found in 

 considerable numbers on Painswick Hill, Gloucestershire, 

 there is but a single pair of these pouches to each of the 

 somites that in the littoral species has two. 



These structures were first observed by Guerin,* who 

 apparently only knew them in their everted condition in 

 alcoholic specimens, and who, from their somewhat 

 similar form and position, not unnaturally regarded them 

 as branchiae, analogous to those of Isopod Crustacea. 

 Burmeister f objects to this interpretation, and considers 

 that they must have some other signification, internal 

 breathing organs — namely, tracheae — being already 

 present. 



In Nicoletia, the abdominal exopodites are said by 

 Nicolet to be "accompagnees chacune au cote interne 

 d'un petit corps, vesiculeux et ovale faisant probablcment 

 partie des organes de la respiration. "| These are, doubt- 

 less, identical Avith the structures observed by Guerin and 

 myself in 31achilis. 



Campodeu^ has five or six pairs of relatively larger 

 glandular pouches. 



I am inclined to look upon these pouches as renal || or 

 segmental organs, especially as I have observed, on the 

 ventral or inner surface of all tlie conical foot-protuberances 

 of Peripatus, in a position therefore answering as nearly as 

 possible to that of the openings in MacJiilis, a slit-like pore, 

 with swollen and slightly-everted mouth, leading, no doubt, 

 into the segmental organsif discovered by Hutton,** and 

 traced by him into the legs. 



The recently-everted pouch in Machilis is covered with 



* Ann. d. Sc. Nat. 183G, p. 37-1. 



t Ilandb. d. Entom., Bd. ii. 1839, p. 455. 



X Lubbock, 'Monograph of Collembola and Thysanura.' 



§ Already observed by Meinert (Ann. Mag. Nat. Hist. 18G7, ser. 3, vol. 

 XX. p. 375). 



II It is a significant fact that no Malpighian vessels have yet been 

 detected in any Thysanuran except Lepisma, in which these glandular 

 pouches appear to be entirely absent; Meinert says, "I have failed to 

 discover Malpighian vessels, nor do I think they exist either in lapijx or 

 in other Thysanura." 



^ The aperture of the apparently homologous slimc-glands, in the embryo 

 of P. capcn&\s, occupy the same position {teste Moseley in Phil. Trans.). 



** Ann. Mag. Nat. Hist. [Two papers on Peripatvs, by Mr. Hutton, 

 are contained in Ann, Mag. Nat. Hist. XVIII. pp. 361 — 309, and XX. 

 pp. 81— S3.— lul] 



TRANS. ENT. SOC. 1879. — PART II. (jULY.) M 



