203 
about the question how these strange spiracles may 
have arisen and how their relation to the normal 
tracheal system is brought about. The appearance of 
such supplementary respiratory organs on the limbs is 
quite unique within the Arthropods. Of course they are 
performing a part of the supply of air of the long, 
slender legs. Dr. Sørensen has verbally put the question, 
if their existence might not be brought in connection 
with the well known and astonishing capacity of the 
limbs of Phalangioide to be able to make violent 
movements a considerable time after they have been 
pulled off from the animal; this vitality should, in that 
way, be connected with the excellent renewal of oxvgen 
which these spiracles are able to furnish to the legs. I 
set forth this idea as a hypothesis to be further proved 
by experiments on living animals; especially it has to 
be tried if the limbs of other Opilionids, as /schyrop- 
salıs, Nemastoma, Trogulus, which are devoid of these 
spiracles, have an equally well developed capacity of 
making movements in a torn state. 
(I cannot quit Opiliones without mentioning that 
Gaubert has neglected to make use of and quote a work 
by W. Sorensen: Om Bygningen af Gonyleptiderne, 
en Type af Arachnidernes Classe (Naturh. Tidsskrift, 3. 
R. B. XII, 1879—80, p. 97—222, pl. Il), although this 
‘paper is of great importance. Gonyleptidee (Opiliones 
Laniatores) constitute a chief-division of Opiliones in 
opposition to Op. Palpatores; the work of Sorensen 
is the only newer complete anatomical monograph of a 
form of Opilionids, and it is not possible to give a 
general representation of a series of structural features 
in Optliones, as Gaubert has tried, without paying atten- 
tion to the one of the two sub-orders. Inter alia we 
find in Sorensen’s papers a detailed representation of 
the structure of the integument, the segments of the body 
