50 Prof. Allman on a new genus and species 



beneath the integument from a point close to the spiracular orifice, 

 to within a short distance of the mesial line of the under surface 

 of the abdomen, may be observed a dark-coloured and very evident 

 line (fig. 2 k). This line, which I believe we would be right in 

 interpreting as a tube, terminates at its end nearest the spiracle 

 in a pyriform cul tie sac (fig. 2 / & fig. 9), and at the other in a 

 conical or infundibulate expansion (fig. 2 m), through which it 

 would seem that the tube opens externally into a remarkable 

 pouch which extends across the anterior part of the under sur- 

 face of the abdomen from the conical termination of one tube to 

 that of the other, and easily admits the introduction of the point 

 of a needle (fig. 10). The cul de sac of the tube contains a some- 

 what pyriform curved organ marked with circular or spiral stria? 

 (fig. 9 a), and a careful examination will detect certain filiform 

 organs extending from the tube in the greater part of its length 

 backwards till lost among the contents of the abdomen. Whether 

 however these filaments are csecal appendages opening into the 

 tube or muscular fibres, or something quite different from both, 

 is far from evident. This portion of the organization of Hal- 

 arachne I have preferred describing as referable to the generative 

 system, though its exact function must still be viewed as hypo- 

 thetical. Among the numerous specimens I have examined I 

 could detect no traces of distinction of sex ; all appeared to pos- 

 sess precisely the same structure and all to be reproductive. Hal- 

 arachne would seem to be viviparous, for the rupture of the walls 

 of the abdomen would frequently liberate the young furnished as 

 yet with only six legs, and the abdomen scarcely visible, but in 

 other respects the embryo to all appearance in rather an advanced 

 stage of development. In what special organ these embryos are 

 confined previously to parturition, or through what opening they 

 naturally escape from their parent, I am unable to form any satis- 

 factory opinion. 



Small six- legged mites (fig. 11), most probably the larva? of 

 Halarachne, and apparently differing but little in form from the 

 embryo condition just alluded to, may be found in considerable 

 abundance along with the adult animal. 



In these the abdomen is but little developed. The legs scarcely 

 differ from those of the adult except in number and in being 

 proportionably longer ; they are all furnished with the double 

 claw and intermediate caruncle. The oral organs seem also to 

 approximate nearly to the condition already described. Neither 

 dorsal plate nor plastron of the cephalo thorax is evident. 



The internal anatomy may in some respects be studied with 

 greater facility than in the adult. The alimentary canal com- 

 mences in a straight and delicate tube, which after passing above 



