ELISHA MITCHELL SCIENTIFIC SOCIETY. 91 



equal length and diameter with the inside of the egg membrane. 

 It next begins to elongate and become more slender. This forces 

 it to double up inside the egg membrane. It does so by turning 

 its tail end by degrees around to its ventral side (Figs. 11, 12). 

 In some cases the tail end for a time does not move. This causes 

 the embryo to double up midway, and sometimes to be coiled in 

 a spiral manner for awhile. It now continues to elongate until 

 it is coiled twice (Fig. 13), then three times (Fig. 14), and finally 

 four times (Fig. 15), within the egg membrane. 



I have watched the egg and embryo, under the microscope, pass 

 through all these changes. Sometimes the embryo would double 

 its length in eight or ten hours. When it has reached this stage 

 it remains a day or so still within the egg membrane while the 

 cuticle, the tough transparent body wall, is being perfected, and 

 the slender pointed end of the tail is formed. Now by its 

 writhing and twisting it ruptures the tough egg membrane and 

 is set at liberty. At this stage the larva passes through its first 

 moult, either just as it is coming from the egg membrane or 

 very soon afterward. Fig. 16, Plate IV, represents the larva 

 in the act of coming from the egg membrane. It is moulting 

 at the same time. The thin larval skin can be seen slipping off 

 its head and tail. 



As the female remains in a cystic state and the cyst is sur- 

 rounded by the tissues of the plant the eggs when crowded in 

 the uterus rupture it and finally the numbers of them completely 

 fill the body cavity of the cyst. In a few cases, after freeing a 

 cyst, I have observed eggs pass out at the vulva. 



Segmentation of the egg begins before it leaves the uterus, and 

 we find, in the body cavity of live female cysts, eggs in all stages 

 of development, and free larvse, so that the female may be said 

 to be ovivi parous. 



Larval Stage. — The larval stage begins with the hatching 

 from the egg. The moult which takes place at the same time is 

 the first moult of the larva. The young thread-like worm is 

 from .3 mm. to .4 mm. (twelve to sixteen thousandths of an inch) 

 long; it tapers gently to the blunt head end, and gradually into 



