NEMATODE DISEASE OF WHEAT. 19 



tive organs. The latter extends as a tube of about uniform diam- 

 eter nearly up to the esophagus, folds back for a short distance, and 

 terminates in a closed end. This tube is usually well filled with 

 developing or mature spermatozoa, which with the aid of a copulat- 

 ing organ, the spicula, located near the sexual opening, may be 

 ejected during coition. Unlike the intestine of the female and 

 similar to that of the larvse, the intestine of the male extends, largely 

 undisturbed by the reproductive system, from the base of the eso- 

 phagus nearly to the anus as a tube of uniform diameter. 



The male is capable of movement during practically its entire life, 

 retains its larval shape, and probably copulates only once. Slug- 

 gishly moving males are often found in galls which contain only 

 the shapeless disorganized remains of females. As has been stated, 

 males and females occur in about equal numbers. 



EFFECT OF HIGH TEMPERATURES ON THE LARV^. 



LARViE INSIDE OF THE GALLS. 



In order to determine the maximum thermal death point of the 

 larvse, the writer has treated a large number of galls with hot water 

 at various temperatures. The results of these tests are presented 

 in Tables I and II. Galls soaked several hours or days in unheated 

 tap water were used in obtaining the data given in Table I, while 

 in Table II the data were obtained from treating the dry mate- 

 rial. In all cases the same method was used in applying the hot- 

 water tests. It consisted in submerging lots of two to six galls for 

 the desired length of time in a large volume of water, the tem- 

 perature of which did not vary during the course of the experiment 

 more than 1 degree above or below that required, and usually varied 

 less than half a degree in either direction. Following the treat- 

 ment, each gall was placed in distilled water in a Syracuse watch 

 glass, then carefully opened with sterilized instruments, and the 

 larval contents microscopically examined repeatedly for several days 

 afterward. In the first few experiments larvae were discarded after 

 having been under observation for one day subsequent to treatment, 

 but it was soon discovered that some of the organisms showed signs 

 of life at a later date, so in all succeeding experiments the larvse 

 were observed over a period of two to nine days. A total lack of 

 movement of the larvae in combination with the coagulation of their 

 internal granular contents was taken as the criterion of death. The 

 largest number of larvse found to be living while they were under 

 observation was roughly estimated in the percentage of the average 

 number of individuals (about 1,500) contained in each gall. All the 

 nematode galls used in these tests were from the same source, namely, 

 a collection made on a farm near Union Mills, Va. 



