134 p. MANSON ON MICRO-FILARI^, WITH 



" Female. — Length varies very considerably — about 1 J'^isthe average. 

 Greatest diameter, un impregnated, yIj" • 



Ditto ditto, impregnated, -g^^". 

 Anus, ^^-g" from caudal extremity. 

 Vagina, infundibuliform, opens y-^^" from mouth. 

 Mouth CESophagus and alimentary canal as in male. 

 Uterine tubes unite anteriorly to form vagina which runs 



forward in a straight course. 

 Expressed embryos measure -^-i^^" by 33^0"; they are 

 naked and have truncated tails. 



" Free embryos. If one examines the blood of the magpie, there 

 is usually no difficulty in finding plenty of embryos, and at first 

 sight seemingly of two different kinds, one minute species, ^^" by 

 •g^Vjr" or thereabouts, the other larger, y^^" by ;5-^^-oo"- The 

 smaller are languid, the larger active in their movements. A jerk- 

 ing, pouting, oral movement is characteristic of both. In both the 

 mouth seems quite simple and the tail sharp and pointed. In 

 neither have I seen any trace of lash or double outline. Betwixt 

 the extremes of length I have given, intermediate sizes can usually 

 be found. Neither extreme corresponds exactly with the dimen- 

 sions of the embryos in the vagina of the presumed parent. There 

 is also considerable variation in the breadth of the smaller speci- 

 mens. Query — Do the embryos found in the blood belong to the 

 same species, and are they thus early commencing development and 

 separation into male and female ? Last December I examined a 

 female parent from the heart-valves, and found in her vagina em- 

 bryos of t^^-q" by -gTjV^'', and having truncated tails. In the same 

 bird were two male worms, and another unimpregnated female. I 

 found no large free embryos in the bird's blood, only numerous 

 small ova very short and very stout, -^^^" by -s-qqu" ; therefore, if 

 the valve worms were the parents of the embryos free in the blood, 

 their offspring must have diminished in length, increased in breadth, 

 and have had their tails sharpened. And if the larger specimens 

 of free embryos are also the progeny of the valve worms, they too 

 must have had their tails sharpened and grown in length at the 

 same time. 



" You will require to use great gentleness in removing the worms 

 from their cysts, as they are very delicate and easily broken. I 

 have half extracted the wonii in some instances as a guide to the 



