150 



The Journal of Heredity 



ing from 43 to lU-i mm. Hagmeier 

 gives for the males of Ag. albicans a 

 length from 29 to 80 mm., for the fe- 

 males 38 to 330 mm. Occasionally 

 very small females may also be seen 

 in this species exceeding in length only 

 slightly, or not at all, the average male. 

 Unusually large males have also been 

 observed, attaining the length of the 

 smaller females. While the size may 

 therefore have a certain value in deter- 

 mining the sex of individuals the gonads 

 and copulatory organs are nevertheless 

 the chief characters. The female sexual 

 opening, the vulva, is a narrow trans- 

 verse fissure near the middle of the 

 body. It leads into a tubular vagina 

 opening at right angles into the uteri. 

 They are outstretched, one forward the 

 other backward, and merging through 

 the oviducts into the ovaries (Fig. 1). 



The male sex opening, however, is 

 situated near the tail end, and com- 

 bined with a copulatory apparatus con- 

 sisting of two cutinized spicula and the 

 muscles needed to move them. The 

 ductus cjaculatorhis, succeeded by the 

 vas deferens, leads to two testes of 

 which the one is outstretched forward 

 and the other backward. Furthermore, 

 so-called bursal muscles are present in 

 the tail end of the male on each side 

 a left hand and a right hand series. 

 They are slightly inclined to the body 

 axis and by their action the tail end 

 of the male is enabled to embrace in a 

 spiral manner the l)ody of the female. 

 Besides these organs there are numer- 

 ous papillae on the male tail end, 

 being the endings (»f nerve fibres, as 

 shown in Figures 1 and 3. 



Thus the organization of the female 

 Ag. dccandata, is distinctly different 

 from that of the male. Hagmeier ol)- 

 served another difference between males 

 and females of Ag. albicans, namely. 

 the size of the amphids (Cobb) or 

 lateral organs, which he says are small- 

 er in the female than in the male. In 

 our specimens we were not able to ob- 

 serve this distinction. 



The intersexes observed in .\merican 

 Ag. dccandata and now about to be de- 

 scribed, are, as alreadv mentioned, all 



n 



FREE-LIVING LARVAL FORM 



Figure 4. The first larval stage of Ag. 

 dccandata is free-living, while the second 

 larval stage is parasitic upon grasshoppers, 

 roaches and possibly other insects. When 

 the larva enters the host or shortly after- 

 ward about five-sixths of the body is 

 dropped and only the head end (a, in figure) 

 continues to live and grows into the adult. 

 Division of the body takes place at a pre- 

 formed node (;;). This is one of the most 

 remarkable cases of self-amputation known 

 and was first observed by Dr. N. A. Cobb. 

 It shows that the part of the alimentary 

 tract that is homologous with the rectal and 

 anal regions of other nematodes (r, in 

 figure), is dropiped in this species. There- 

 fore what openings occur at the tail-end of 

 the adults can only be regarded as sex open- 

 ings and never as anal openings. 



females. They all have complete nor- 

 mal female sex organs and most of 

 them normal eggs in the uteri, and all 

 were found encoiled and copulating 



