Eraerton.] 



506 



[April 21, 



The true structure of the palpal organ is best seen in some large 

 species of Mygale, where it consists simply of a hard bulb, prolonged 



Fig. 1. 



into a hollow penis, Fig. 1. Within the bulb is a sac, attached by its 

 base to the side of the bulb at a, and narrowed at the other end into 

 a tube b, which leads to the orifice of the penis c. In other spiders 



the essential structure of the palpal 

 organ is the same, though often ob- 

 scured by the spines and appendages 

 of the bulb, and modifications of the 

 shape of the tarsal and tibial joints of 

 the palpus. In almost all species the 

 tarsal joint is flattened and hollowed 

 on the fe under side, to receive the 

 shortened and twisted bulb. The 

 simplest case of this is seen in Attus 

 tripunctatus, and several other species 

 of Attus, where the penis is a short, 

 blunt tube, and the bulb flat, smooth, 

 and without appendages. Where the 

 penis is long it is almost always ac- 

 companied and supported by a thin, 

 flat process of the bulb, called, by 

 Lyonet, the conductor, as in the palpi 

 of Dictyna, figured by Lyonet, in the 

 American species of the same genus, 

 in Tegenaria medicinalis, Clubiona pal- 

 lens, and many others. In most Epeirse the penis is short, and 

 accompanied by several large processes, as in Epeira vulgaris Hentz, 

 Fig. 2. This latter figure represents a palpal organ made transpar- 



Fig. 2. 



