528 
W. V. PUECELL. 
minuteSj washed with spirits, and then held inverted over a 
vessel containing a drop of ammonia in some water until the 
sections change colour. After this they should be mounted 
in balsam without delay. The nuclei become blue and 
the muscles reddish and easily distinguishable from other 
tissues. 
In preparing the tracheae by the caustic potash method I 
obtained the best results for such highly complicated systems 
as those of Caponia by first allowing the object, after 
removal of a part of the dorsal integument, to remain in cold 
concentrated caustic potash for twelve hours or longer. If 
the solution be then gently heated and some water added the 
soft parts remaining will rapidly disappear without injury to 
the delicate trachem. These should be examined in water or 
weak alcohol, and not in glycerine or acetate of potash, since 
these latter cause the tubes to collapse and become distorted. 
The Kespieatory Segments op the Dysderid.®, Oono- 
PIDA5, AND CaPONIID.E. 
These spiders more nearly resemble the My gal o morph a? 
than they do the rest of the A rachnoniorphge in the 
anterior position and wide separation of the second pair of 
spiracles (sp"., text-figs. 3 — 5) and the more rudimentary 
condition of the ectodermal tendons (where present) of the 
second respiratory segment. 
Further, the transverse epigastric fold, lying between the 
two anterior spiracles, although present, never encloses a 
spinous canal of communication connecting the lumens of the 
two anterior respiratory organs, while the Dysderidm are 
unique amongst arachnomorphous spiders in having no inter- 
tracheal fold between the two posterior spiracles (text-fig. 3), 
a primitive character only met with elsewhere in the 
Mygalomorphae (p. 524, text-fig. 2 ). Owing to the presence 
of trachem instead of lung-books in the ninth somite this 
segment is somewhat shortened, but in other respects the 
