100 INTERNAL ANATOMY OF INSECTS. 



Clubiona atrox, it is without them a . It exhibits a pair of 

 vessels that appear to connect with the gills, by which 

 the oxygenation of the blood takes place, and a number 

 of others that ramify minutely and are lost in the ana- 

 logue of the epiploon, supposed to be their liver b . Whe- 

 ther these last are to be regarded merely as veins, has 

 not been ascertained ; ftiey seem rather to convey the 

 blood outwards, than to return it back to the heart : but 

 this question must be left for future investigation. I may 

 observe, however, that though the heart of the spider 

 has been traced only in the abdomen, it may probably ex- 

 tend into the trunk. 



The heart of the scorpion has been examined both by 

 Treviranus and Marcel de Serres ; but I shall principally 

 confine myself to the description of the latter, as the 

 most clear and intelligible. The heart, then, of these 

 animals is elongated, almost cylindrical, but attenuated 

 at each end ; it is extended from the head to the extre- 

 mity of the tail, and appears to have four pairs of lateral 

 muscles. On each side are four pairs of principal ves- 

 sels, which go to the pulmonary pouches, and there 

 ramify. These may be assimilated to veins. Besides 

 these, there are four other vessels that cross them, form- 

 ing with them an acute angle, and which, with four 

 branches of smaller size, receive the blood from the pul- 

 monary pouches, and distribute it to the different parts 

 of the body, these are the arteries. Before it enters 

 the tail, the heart throws out two vascular branches 

 which do not go to the gills, but distributing the blood 



a Treviranus Arachnid. 2$. t. iii./. 28, 29* 

 b Ibid. 29. /. iii./. 30, 31. 



