88 



THE LARVA OF THE BLOW- FLY. 



Viallanes [27, p. 66] describes the dorsal vessel of a young 

 dipterous larva, which he refers to the genus Ctenophora, in 

 which he observed tufts of fine tracheae in the pericardium, and 

 the connection of the dorsal vessel with the transverse anasto- 

 motic tracheal trunk. He adds : 



IMG. 18. The dorsal vessel: i, a semi-diagrammatic representation of the two 

 posterior sections, showing the large cells of the pencardial septum, the alse 

 musculares and the) cell fringes ; 2, the anterior extremity of the aorta and the 

 rm g ; 3, a transverse section of the intermediary portion ; 4, a longitudinal sec- 

 tion of the same, with a pair of valves, seen from above, showing the internal 

 cells, cell fringes and alre musculares ; j, a lateral vie\v of a valve pouch jV oil 

 immersion lens. 



' It appears, therefore, that in this larva the dorsal vessel is 

 an'Farterial heart, since the blood which enters it has passed 



