The Internal Anatomy of Spiders 



The more general features of the heart of different types of 

 spiders are represented diagrammatically by the drawings in 

 Fig. 1 58, which are based on a series of figures given by Causard 

 ('96). The first drawing (1) represents the heart of a four-lunged 

 spider; the second (2), the usual form of the heart in the two- 

 lunged spiders; and the third (3), the heart of Dysdera. The 



I 2 3. 



Fig. 158. DIAGRAMS OF HEARTS OF SPIDERS (after Causard) 



heart is somewhat enlarged toward the anterior end and tapers 

 toward the posterior end. From the anterior end extends the 

 aorta (a); from the posterior end, the caudal artery (ca);and from 

 its sides, the lateral abdominal arteries (la). The cavity of the 

 heart is more or less expanded at regular intervals, forming 

 paired diverticula, from which the arteries arise. The wall of 

 the heart is pierced by a series of paired openings, the ostia 

 From the heart extend a considerable number of strands, the 

 cardiac ligaments (cl). At some distance from the heart, but 



149 



