144 
the Acari. Some authors (Haller 7 and Oudemans 17) do not 
at all regard the Acari as Arachnids and are consequently unable 
to compare their mouth parts with those of the other Arachnids. 
Others and among those A. Michael (10) has neither taken part 
with the one nor with the other, while he is disposed to make a 
comparison with the Insects. Still others as Winkler (20), 
Brucker (3), Bårner (4) homologize the different parts of the 
mouth organs with those of the other Arachnids, even if they do 
not agree in details; this last point of view is certainly the only 
correct one. 
The most developed pseudocapitulum (f. inst. in the Gamasidae) 
is a tube formed by the fusing of the ,,rostrum”, — which in reality 
is nothing but the front part of the head with the maæil/ae. In 
other Acari the ,,rostrum" is only a bridge covering the basal part 
of the antennae. In the Bdellidae (Michael 14) and Noerneria 
(Nordenskidld 16) the antennae are uncovered in their whole 
length. The sides and the lower part. of the pseudocapitulum are 
made of the måxillae fused with each other in the middle line. 
The palps are articulated with the måxillae, which probably are n0 
other thing than their coxae. The distal part of the maxillae is 
mostly free and developed in a different manner in the different 
families. 
The question if the ventral side of the pseudocapitulum is only 
formed by the maxillae or by the coalescence of the maxillae with 
a labium, has been answered in a different manner by the different 
authors. Brucker startes the theory that there exists a ,,;tégument 
post-oral virtuel" (2 pag. 417), which in connection with: his ,,tégu- 
ment supra-oral" (basal part of the labrum) forms ,,/a trompe 
pharyngée", including. the pharynx; to prove this theory worked out 
into its consequences he advances more of common meditations than 
convineing facts. C. Borner (4 pag. 108) agrees in the principal 
points of view with the said naturalist, though his theory is founded 
on a more common arachnological base, making a comparison be- 
tween the Pedipalpi and the Acari. Winkler who regards the 
