306 PROCEEDINGS OF THE ACADEMY OF 



These homologies might be shown tabularly as follows : 



[May, 



Spinnerets. 



Liphistiidse. Antero-lateral. 

 Aviculariidse. 



Aranese 

 verse. 



Anterior. 



Antero-median. 



Colulus or 

 cribellum. 



Postero-lateral. 

 Posterior. 

 Posterior. 



Postero- 

 median. 



Median. 

 Median. 



2. Development of the Trache.e. 



Locy (1886), the first to mention the development of these struc- 

 tures, simply states that "upon the ventral surface appear the infold- 

 ings, from which are formed the tracheae." Schimkewitsch (1887) 

 is mistaken in saying that Balfour (1880) demonstrated the origin of 

 tracheae and lungs, for Balfour did not mention these organs. Schim- 

 kewitsch briefly mentions a stage in Lijcosa before hatching where the 

 tracheae are already branched. Kishinouye (1890) writes: "In the 

 basal part of the second abdominal appendage, on the interior side, 

 another ectodermic invagination is produced. It assumes the shape 

 of a deeply invaginated tube and remains in this condition till after 

 the time of hatching. The appendage itself is not invaginated and 

 becomes from this time gradually shorter." Purcell (1895) states 

 that the " entapophyses connected with the second (tracheal) pair 

 of appendages become each drawn out into a long tube, to or near the 

 blind, inner end of which the middle pair of endosternites is attached 

 in the adult. These long tubes are represented by the two large 

 trunks which form the tracheae in the Attidae, and by the medial pair 

 of the four trunks which compose the tracheae in most other Spiders 

 (Agelenidae, Drassidae, Epeiridae, Lycosidae, etc.)." 4 



The preceding references to the tracheae are all brief and not illus- 

 trated by figures. Simmons (1894) goes into the subject somewhat 

 more fully; he finds the tracheae arising before reversion behind the 

 appendage of the third abdominal segment as a tubular, ectoblastic 

 ingrowth, and the tube so produced to have an irregular folding of its 



4 My friend Dr. Purcell's brief but important preliminary paper deals mostly 

 with the homologies of the tracheae and entopoyhyses, on which subject he has 

 now an extensive paper in press. I have not considered these relations In 

 Loxosceles I find just latero-posterior to each appendage of the four anterior 

 abdominal pairs a thickening which appears darker than the surroundings on 

 stained surface views, these being marked x in figs. 20-24 of PI. XIII. I have 

 not determined whether these are apophyses or simple muscle insertions. 



