Steiner: Intersexes in Nematodes 



155 



TAIL ENDS OF NORMAL MALES 



Figure 10. In addition to the variation 

 in the head organs of this species, other 

 normally constant characters are unusually 

 variable. This shows the tail ends of two 

 normal males of Ag. dccaudata. Note the 

 considerable variation in the position and 

 number of the papillae. These differences 

 are greater than are found m other species 

 of nematodes. 



probably chemical sense oi"gans. These 

 organs are of very constant nature in 

 nearly all nematode species, and the 

 amphids, or lateral organs are especial- 

 ly of high value as specific characters. 

 In the Mermithidae this is particularly 

 true. The adult specimens may be 

 identified more or less easily by the aid 

 of the sex organs, but the larval speci- 

 mens can only or best be distinguished 

 bv the sense organs of the head. The 

 position, the size, and the structure of 

 the amphids is very different in differ- 

 ent species of Mermithidae, although 

 within the species, with few exceptions, 

 very constant. Such exceptions are 

 Ag. dccaudata and related forms. The 

 number, the structure and the position 

 of the amphids varies here very much, 

 but other significant and easily percep- 

 tible diff'erences have not yet been dis- 

 covered. There are differences also 

 in the shape of the tail end, but these 

 are insignificant. Perhaps the number 

 of metabolic cells along the esophageal 

 tube may be of taxonomic use if more 

 were known about them. 



Fioure 9 shows the head ends of 



specimens of Aij. dccaudata, all differ- 

 ing from each other in respect to the 

 amphids. Why in this form are the 

 amphids so inconstant, while they are 

 so constant in most of the other nema- 

 todes? Is it not that we have in Ag. 

 dccaudata and related forms, not sharp- 

 cut species, but an association of dif- 

 ferent races or genotypes and numbers 

 of hybrids between them? These races 

 are perhaps continually crossing and it 

 is thus that such a multitude of struc- 

 tural forms in the head end comes 

 about. The numerous intersexes are 

 another result of these crossings be- 

 tween closely related genotypes. In 

 the light of the experiments of Gold- 

 schmidt and the other above-mentioned 

 investigators, where intersexes resulted 

 from hybridization of closely related 

 forms, it is highly probable that there 

 is a causative relationship in this case 

 between the numerous related species 

 and races, and the number of inter- 

 sexes observed. Yet this is only an ex- 

 planation which seems to give most 

 satisfaction, and could not be accepted 

 as final until the matter has been tested 

 by experiment. 



More recent experiments point to 

 the same conclusion. What was for- 

 merly called Mcnnis albicans by dif- 

 ferent authors is perhaps a group of 

 morphologically closely related forms. 

 It may be that they are species, or at 

 least races. One of these may perhaps 

 be our Agamcruiis dccaudata, which in 

 the adult stage reseml)les to a high de- 

 gree the former species and was ap- 

 parently taken as such by Leidy and 

 other authors. Experiments by T. R. 

 Christie and the writer show that the 

 larvae of this latter species ( dccau- 

 data), could not be brought to infest 

 other animals than grasshoppers and 

 roaches. Yet this form very much re- 

 sembles the former, which is said by 

 many writers to parasitize insects of 

 the most various groups, and even 

 snails. 



All these facts, it seems, are good 

 evidence that the numerous intersexes 

 observed as normally forthcoming in 



