1909.] NATURAL SCIENCES OP PHILADELPHIA. 299 



ON THE SPINNERETS, CRIBELLUM, COLULUS, TRACHEJE AND LUNG BOOKS 



OF ARANEADS. 



BY THOMAS H. MONTGOMERY, JR. 



This paper presents observations on the ontogeny of the organs men- 

 tioned in the title, together with notes on the anatomy of the cribellum 

 and colulus and with certain considerations on the broader mor- 

 phological relations of these various organs. 



The embryos of the spiders examined were killed in Carnoy's fluid 

 (absolute alcohol, chloroform and glacial acetic acid in equal parts, 

 with corrosive sublimate to saturation), an excellent fixative that 

 makes it possible to cut with ease good series of paraffine sections; 

 it has the disadvantage of frequently producing an extra ovat of yolk 

 in the earlier stages. After fixation and hardening the egg membranes 

 are readily removed with needles. In order to secure good surface 

 views of the abdomen after the stage of reversion it is best to cut off 

 the cephalothorax, and with a knife to remove a considerable portion 

 of the abdomen itself so as to allow the stain (preferably Delafield's 

 hsematoxyline) to penetrate evenly. The adult spinning organs 

 with the cribellum or colulus are best examined in balsam after 

 dehydration and clearing, and after the dorsal half of the abdomen 

 has been cut away. Of Theridium tepidariorum and Loxosceles 

 rufescens I secured accurately timed stages by breeding females in 

 captivity. The material of Theridium was collected by me at Woods 

 Hole, Massachusetts, and thai of Loxosceles, Evagrus and Filistata 

 hiberncdis at Austin, Texas. I am obliged to Mr. Nathan Banks for the 

 determination of these species. 



1. Colulus, Cribellum and Spinnerets. 



The first question to be taken up is the matter of the morphological 

 relations of the colulus and cribellum to the spinnerets. 



According to the classification of Simon (1892) two main groups of 

 the Aranese are distinguished: the Aranese theraphosse and the Ara- 

 nese verse. The former include the families Liphistiidae, Aviculariidse 

 and Atypiclse; of these the first are unique among all spiders in the 

 possession of four pairs of true spinnerets (mammillse), while most 



