Exo'etorji Orf/ans In Condf/lopodn 51 



But in Crustacea, that class of Condylopoda, to which in o>u' view Arachnida are 

 more nearly allied than to any of the other classes, the excretory organs open, as is well 

 known, on the outside itself of the body ; but neither in this case are they fidly homologous 

 throughout the class, because in Malacostraca (with Nehalia) and at any rate Gythere they 

 open on the second pair of antenna\ whilst the " shell ^land " in Phyllopoda and Cumacea 

 opens at the second pair of maxilla^. 



In Insects and Myriopoda the excretory organs are the Malpighian tubes, which, as 

 is well known, are always connected with one and the same part of the body, viz. the 

 last segment of the latter, opening as they do in that purtion of it which is turned 

 inwards and forms the rectum '. 



The fact therefore is that in all Comlylopoda the excretory organs open on the surface 

 of the bodj- (the skin or ectoderm), but belong to different portions of it in different 

 groups. We cannot therefore consider them fidhi h(jmologous organs throughout the series, 

 nor even in all groups of Arachnida. 



1 1 . Organs of Respiration. 



Cyphophthalmi, as indeed Opiliones generally, possess one pair of tracheae which are 

 ramified into very numerous branches and supplied with filiform spiral thickenings, and 

 W'hich open on the apparently first, really second abdominal sternite. In all Cyphophthalmi 

 with which we are acquainted the spiracles are plainly visible on the ventral surface of 

 abdomen. They are shaped like a narrow band, more or less curved, so that in Siro the 

 ends almost touch each other whilst in Sti/locellus (Beccarii) the spiracle (PI. I., fig. 1 n, b) 

 is formed like a somewhat irregular semicircle. The bridge between the skin enclosed by 

 the spiracle and the skin around it is directed backwards, as in Siro, or at the same time 

 somewhat outwards, as in Purcellia. Although we have not succeeded in forming a clear 

 conception of the extremely complicated structure of the spiracles in the few specimens 

 which we have been able to examine, we may affirm that they are always latticed, that 

 is to say furnished with close transverse bars across their opening. 



In Laniatores the spiracles are never yawning openings ; in the great majority of them, 



at any rate, they are of the type described by Sorensen in the first representatives of this 



sub-order examined by him (6, p. l-iO, PI. II., fig. 14), viz. sefnilunar, latticed, the crossbars 

 being furnished with small closely placed tuberosities. 



base of the third pair of limbs, but at the same time he was that part of the alimentary canal which is formed by the 



able to prove the existence of such at the bases of the fourth entoderm. With regard to Aranea? we may refer to a short 



pair of limbs at an early stage of development. These latter but very interesting paper by Loman (6) in which he has 



were only in a rudimentary state and very soon atrophied. placed it beyond doubt, that in that order the tubes in 



It will be seen that Gough's observations afford a further question open into the mid-gut, not into the rectum, and on 



proof of the correctness of our view. this ground maintains that they are not real Malpighian 



' It is very doubtful whether organs which fully eoiTe- tubes. Wagner has already (p. 137) emphatically maintained 



spond morphologically to the Malpighian tubes in Insects that Arachnida upon the whole do not possess organs that 



occur at all in any Arachnida. Certain slender tubes which are the homologues of the Malpighian tubes in Insects. We 



open into the alimentary canal in Arane* and others have are incUned to adopt this view, but are of opinion that it is 



been looked upon by earlier authors as homologous with the perhaps a little too soon to consider it fully established 



Malpighian tubes in Insects, but more recent writers at any before it has been decided what character the structure 



rate are more inclined to think that they are connected with has in certain Acari. 



