RESPIRATORY ORGANS IN ARANE.E. 
1 
Development and Origin of the Respiratory 
^ Organs in Aranese. 
By 
\V. F. Fiiiooll, Pli.D., 
Bei'^vliet, Diep Rivei’, near Cape Town. 
With Plates 1 — 7 ami T Te.xt-fignres. 
CoNTKNT.S. 
I. Introduction . . . . . 
Material . . . . . 
Biological Observations . . . . 
Treatment .... 
II. General Orientation . . . . 
Ining-hooks . ... . 
Tracliea; . . . . . 
III. Historical (Development) . . . . 
Development of the Lung-books in Arachnida. 
Development of the Trachea; in Aranese 
IV. The Provisional A1)dominal Appendages in the Embryo 
of Attus floricola 
V. The Development of the Lung-hooks . 
Stage with two Pulmonary Furrows 
Stages with three or more Pulmonary Furrows 
Formation of the Spiracle . . . . 
Sinking of the Apj^endage 
Formation of the Pulmonary Saccules 
Comparison with the Gill-hooks of Limnlus 
Later Development of the Pulmonary Saccules 
The Chitinous Lining of the Pulmonary Saccules 
The Moidting of the Lung-hooks 
The Operculum of the Lung-hooks . 
The Lung-hooks of the Young Spider 
Critical Remarks on the Literature 
The Fully Developed Lung-hooks of Spiders . 
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