395 



muscles. Some die within the stomach. In the 

 muscles the cuticular striation disappears, move- 

 ment ceases, and the body becomes thicker. 



Second Stage. — For two to three days the 

 embryo becomes much thicker, and the moutli 

 begins to be faintly indicated. 



Third Stage. — An anus appears in front of 

 the tail, and a mouth is very distinct with four 

 fleshy lips. Cells are seen in the body, and 

 these form an alimentary and tegumentary layer. 

 The embryo is now about o"3 mm. long. 



Fourth Stage. — Rapid growth takes place, 

 and the tail becomes relatively smaller. 



Fifth Stage. — Lengthening takes place. The 

 whole worm becomes fibrous and transparent in 

 appearance. It has cast the cuticle. Some large 

 cells at the end of the tail form papillae which 

 are characteristic of this stage of the larva. 

 The parasite is now about i"5 mm. (one-six- 

 teenth inch). Time, about seventh day. 



Sixth and Seventh Stages. — Movements become 

 more active and, when the filariae have reached 

 their highest stage of development in the thoracic 

 muscles, they leave that tissue and travel forward 

 in the direction of the head of the mosquito 

 (Low and James). They reach the loose tissue 

 about the salivary glands and pass into the 

 neck. Some are found in the abdomen. Num- 

 bers of the filaria larvae enter the lower part of 

 the head, lying beneath the large head ganglia. 

 Eventually one or more worms pass into the 

 substance of the labium, where they are readily 

 found by dissection. The larva at this stage 

 measures about one-sixteenth inch in length. 



