PHYSIOLOGY OF THE LWERTEBRATA. 



195 



Mr, A, H. Swintou* has also observed a ventral vessel 

 (Fig. 41) beneath the intestines in Sphiiu Ligiistri. This 

 vessel is contractile like the dorsal vessel, and unites with the 

 latter at the junction of the thorax with the abdomen. At 

 this junction there is a dilatation of a flat-roundish form. 

 Swinton states that there is a twofold alternatinfic pulsation 

 in this dilatation, that indicated a circular flow of the fluid, 



vessel 



Fig. 41. — Circulation ix thk Abudmen of Sphinx. 

 [After SwiXTON.) 



A — heart. /> = dorsal vessel. C = ventral vessel. (Z = afferents. 

 .S = intestines, i — tracheae. 



as shown by the double-headed arrows (Fig, 41) ; and which 

 appears to be a rudimentary heart, composed of an auricle 

 and a ventricle, such as exists in the Mollusca. 



The two main vessels have, besides, several afferents, «, a, 

 and those to the lower one seemed to open each time the flap 

 or fold spasmodically moves upwards ; while a central cylin- 

 drical duct (B) passes from the heart (A) ventrally into the 

 thorax, where its rhythmical action, says Mr. Swinton, " could 

 be at intervals seen extending as far as the second annulation, 

 although the forms of its vessels were obscured, from the fact 

 that circulation was already partially stayed in this position 

 of the body. Lastly, the ventral and flat-roundish vessels 

 continued to palpitate vigorously long after the valves of 

 the dorsal vessel had ceased to move." Mr. Swinton considers 

 that he has discovered, in this pulsating flat-roundish vessel 

 and its afferents, the true heart in the Lcpidoptera. 



* Insect Varieti/: its Propagation ami Distributio:i, 1880, p. 39, 



