338 Thos. H. Montgomery. 



rois, J3alfour, Loey and ]\Iorin, but assigned by them to segments one 

 to fonr inclusive, for these writers overlooked the first segment. But 

 other appendages, mostly of smaller size, have been observed. Thus, 

 Claparede saw six pairs in Chthioiia, while Korschelt (1892) found in 

 an undetennined species appendages on the first segment as large as 

 those of the four following segments, and in Agelena slightly devel- 

 oped appendages on the first segment. Then Jaworowsky (1892, 

 1895) noted pairs of a]:)pendages on segments one to eight (the 

 appendages of the first and sixth to eighth segments being very 

 small. I may add that I have found more than four pairs in a 

 species of Loxosceles, on which I intend to report in another paper. 

 The observers rightly conclude that the larger number of appendages 

 denotes a more ancestral condition. 



As to the fate of these appendages there is some conflict of opinion. 

 Balfour (1880) stated that at complete reversion the '"four rudimen- 

 tary appendages have disappeared, unless — which seems to me in the 

 highest degree improbable — they remain as the spinning mammillae, 

 two pairs of which are now present"; and Schindvewitsch (1887) 

 also maintained that the abdominal ap2)endages disappear and that 

 the spinnerets are new formations. Salensky (1871) first showed 

 that the appendages of the second segment become the lung books, and 

 this important discovery has been corroborated by Locy, Morin, 

 Kishinouye, Jaworowsky, Simmons and Purcell. Wallstabe corrobo- 

 rates Simmons' results, but Avithout giving details. Bruce held that 

 "probably two abdominal appendages are invaginated to form each 

 lung book," meaning thereby those of the second and third segments ; 

 but he was mistaken in this and also in identifying a slight fold of 

 the floor of the pulmonary invagination with a pulmonary lamellci, 

 Simmons (1894) and Purcell (1895) correctly described the origin 

 of lung lamellae on the posterior surfaces of the appendages of the 

 second segment, before these appendages have invaginated, but I shall 

 show in another paper that these primary lamellae do not become 

 the lung lamellae of the adult; Jaworowsky (1892) found these 

 appendages to become the opercula of the lung books, and studied 

 (1894) the development of their lamellae at stages later than 

 reversion. The appendages of the third segment were found 



