121 



and is not provided with valves. The upper portion 

 is attached to the dorsum at intervals by suspensory 

 fibres (muscular), so that a festooned appearance is 

 given in longitudinal section. There is, however, no 

 true division into compartments. Laterally large cells 

 (pericardial cells) are arranged throughout its entire 

 extent, and fibres of a muscular nature (alary muscle) 

 pass from the body wall and end in branches in close 

 connexion with the dorsal vessel. 



At the first abdominal segment the dorsal vessel 

 dips down beneath the mesophragma, lying as it does 

 so in direct contact with the cuticle. In the thorax 

 it again arches upwards, and lies between the lower 

 portions of the antero-posterior wing muscles close 

 above the anterior portion of the mid-gut. 



In the anterior third of the thorax it divides 

 into two smaller portions which pass outwards, and 

 coming in contact with the salivary ducts enter the 

 neck. 



Blood spaces without definite walls occur through- 

 out the body. The thorax especially contains large 

 spaces among the muscles, and the complex fat-body 

 which lies between and supports the organ is every- 

 where bathed with blood fluid. 



THE REPRODUCTIVE SYSTEM 



The organs of the reproductive system are : 



1. Ovaries. 



2. Oviducts and common oviduct. 



3. Mucus gland and duct. 



4. Spermathecae and ducts. 



The ovaries occupy a variable position dependent 

 upon the state of their development. In the newly- 

 hatched mosquito they are small bodies lying in the 



