16 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 50. 



Life history. — The eggs containing embryos are passed in the 



urine of infected animals and are apparently ingested by other rats 



in contaminated food or water. In the stomach of the new host the 



shell digests off and the embryos escape. I have 



seen embryos escape from the shell in the vagina 



of the female after the worm had been in normal 



salt solution a short time, and I judge from this 



fact and from the fact that such embryos seemed 



to Hac only a short time that infection must take 



place in a rather short 

 period as a rule, or 

 else the embryo per- 

 ishes. The embryo 

 has a body of almost 

 u n i f o r m thicloiess, 

 terminating in blunt- 

 ly rounded ends, so 

 far as my observation 

 goes (fig. 18) , but pro- 

 vided with a single 

 lancetlike process an- 

 teriorly, according to 

 von Linstow (fig. 19). 

 Von Linstow sug- 

 gests that the em- 

 bryos may bore into 

 the wall of the diges- 

 tive tract and make 

 their way to the pel- 

 vis of the kidney, pos- 

 sibly by way of the 

 blood stream and the 

 renal artery particu- 

 larly. Sexually un- 

 developed individu- 

 als, the males but 

 little smaller than the fig. 1.3.— trichosomoides 

 females, are found in ^rassicauda vui-va 



'_ _ REGION OF FEMALE. 



the pelvis of the kid- enlarged, after 



1 _ 1 i' Ebertii, 1803. 



ney and copulation 

 takes place in the ureters, the females becoming larger and the males 

 entering the vagina. The first male turns about after entrance and, 

 according to von Linstow, is alwa3^s found with its head toward the 

 vulva. The fertilized females pass to the urinary bladder and grow 



"'C^^^/'' 



Fig. 12.— Trichosomoides crassicauda 

 Vulva region of female. En 

 largeu. 



