17 



and .0025 inch in its short diameter. At each end is a valve or 

 lid which drops off when the embryo emerges from the egg. It 

 has been the general opinion among naturalists that the mature 

 eggs of Syngamus were never discharged through their natural 

 outlet during the life of the female, that being rendered impos- 

 sible by the intimate union of the genital organs of the sexes, 

 whereby the outlet of the vagina was completely closed. They 

 believed that only at the death of the worm and disintegration 

 of its body were the eggs set free. That such is not the case 

 in some instances, / knoiv, for I have distinctly seen, under the 

 microscope, with a power of fifty diameters, the eggs pass out at 

 the posterior part of this union in a living pair, just removed 

 from the trachea of a chick. Two or three eggs were discharged 

 at regular intervals, each minute. On close observation there 

 was clearly observed movements of the worm, showing the nat- 

 ural expulsive efforts, followed by the extrusion of the eggs. 

 Now, in about fourteen days after the feeding of earthworms 1 con- 

 taining the embryos of Syngamus, we have, in several later exper- 

 iments, some of which are not herein recorded, observed the per- 

 fect eggs of Syngamus in the excretions of the chicks. These 

 chicks were then killed and the living pairs of Syngami found 

 attached to the mucous membrane of the trachea. Some of 

 these pairs had not yet attained their complete growth, yet the 

 eggs, near the genital outlet, were fully developed. None of 

 them were found dead and their bodies breaking up in the 

 trachea. From these observations we have no doubt that the 

 living worm, contrary to the opinion heretofore entertained, does, 

 during its life, extrude a large number of perfect eggs, but al- 

 ways dies while many yet remain in its body, which are set free 

 when that decomposes. I have never been able to press the eggs 

 out through the vagina in a dead Syngamus. This may be one 

 reason why naturalists have thought they did not pass out when 

 living that way, but I believe all dead animals have their genital 

 passages contracted in the same manner. It has also been the 

 general opinion that the eggs furthest advanced in a mature 

 Syngamus while living and just removed from the trachea of a 

 fowl contain the perfect embryo already moving actively about 

 within the shell. That such is not the case we believe and will 

 briefly give our reasons for this opinion. In experiment No. 8, 

 it will be seen that a chick fed earthworms containing the em- 

 bryos of Syngamus developed the gapes, and in fourteen days 



