The External Anatomy of Spiders 



rests in the concave tip of the cymbium; bui in the specimen figured the bulb 

 has been extended so as to show the parts better; and the embolus and conductor 

 have been separated at the tip. 



In Pachygnatba the tarsus is divided into two distinct parts, which are joined 

 by a movable articulation at the base. The larger part is the cymbium (Fig. 101, 

 cym.) the smaller part, the paracymbium: this is termed by some writers the accessory 

 branch of the tarsus (Fig. 101, p. c). The cymbium and the paracymbium re- 

 semble the other segments of the palpus in the nature of their cuticula and in the 

 fact that they are clothed with hairs. 



THE MORE SPECIALIZED TYPES OF PALPI 



In the development of the bulb of the male palpus in the more specialized 

 families of spiders there has been evolved an exceedingly complicated organ, 

 which is difficult to understand, on account of its small size and the fact that when 



— emb. 



m.d. 



-p. c. 



Fig. ioi. 



GENITAL is I LB OF 



PACHYGNATHA 



EXTENDED 



a. d. 

 m.d. 



b.d. 



Fig. 102. 



EXPANDED BULB OF 



LIXYPHIA PHRYUIANA 



at rest it is compactly folded. Fortunately when such a palpus is boiled in a solu- 

 tion of caustic potash (10%) the bulb expands so that its parts can be seen: and 

 it preserved in glycerine, it remains flexible, so that it can be easily manipulated. 

 I he expanded bulbs figured below were prepared in this way. Even with the 

 best of preparations, it is sometimes difficult to make out the relation of parts; 

 this can be most easily accomplished by the use of a stereoscopic binocula; 

 microscope. 



I he extreme specialization of the palpi of males is marked chiefly by the 

 development of hjsmatodocha, to be described later, and by an increase in the 

 number of distinct parts and appendages oi tin- bulb. I he maximum degree ol 

 specialization is to be found in the \r.inein.e, of which the palpi ol several species 

 of t>,in,:i are described later. I he understanding of the relation of the parts 

 of ilw hu'lh in tbi* genus will be facilitated by a study first ol a more simple form, 

 such .as is found in the Linyphiids. 



1 I I 



