54 THOMAS L. BANCROFT. 



a thing never occurred to me, and is inexplicable except on the 

 supposition that his mosquitoes had imbibed filariated blood on 

 several different occasions. 



In the following details my observations differ from those of 

 others, who have worked at this subject. 



1. Pressure of the cover-glass more particularly and endosmosis 

 are the cause of rupture and escape of material at the anus in the 

 young filarise ; such is not a natural phenomenon ; it will not 

 happen if the thorax be teased out in Miiller's fluid and examined 

 without a cover-glass or with a small piece of cover-glass. 



2. After the meal of blood is digested, the mosquito's stomach 

 and intestine contain no filarise. 



3. The filarise after imbedding themselves in the thoracic muscles 

 lie quiescent until about the fourteenth or fifteenth day, when 

 very slight movements can sometimes be detected. 



4. I have been unable to satisfy myself that the embryo filarise 

 cast their sheaths before leaving the mosquito's stomach ; when 

 seen in the thorax they appear to have lost the long collapsed 

 sheath following tail ; the sheath may however have only shrunk 

 or it may be filled out by the worm, which has already grown 

 longer and thicker ; the tail is peculiar in the early stages, which 

 may be due possibly to retention of the sheath. 



5. The filarise, which emigrate to the thorax, do so directly they 

 are withdrawn from the human host ; those that are to be seen 

 in the mosquito's stomach several hours later are they, that for 

 some reason, whether being too young, or from injury or from 

 having been already acted upon by the digestive juices, are not 

 destined to enter upon a metamorphosis. Loss of sheath, striation 

 of body, changes in the body protoplasm in them are due to 

 endosmosis and digestion. 



6. No apparent sheath can be seen in the embryo filarise in 

 freshly drawn blood, but a flagellum-like body generally following 

 the tail (Fig. 1); sometimes the flagellum-like body is momently 

 protruded from the head, and pari passu disappears from the tail; 



