INTERSEXES IN NEMATODES 



G. Steiner 

 Bureau of Plant Industry. U. S. Dcpartjncnt of Agriculture, Washiugtoii, D, C. 



STIMULATED by the experi- 

 ments of Goldschmidt on the 

 Gypsy Moth the writer carried 

 out extensive experiments in the win- 

 ter and spring of 1931-23, in which 

 he attempted to cross several morpho- 

 logically closely related free-living 

 nematode species/ The chief aim 

 was to see if intersexes (as the term 

 is used by Goldschmidt) could be 

 produced by hybridization of certain 

 easily reared species. 



Intersexes are individuals which pos- 

 sess the sexual characters of one sex 

 mixed with the characters of the other. 

 Such cases have been long known and 

 some of them were designated her- 

 maphrodites, gynandromorphes, etc. 

 Modern experiments have showed that 

 whole series occur in which the char- 

 acters of a male and female are more 

 or less mixed, thus re])resenting all pos- 

 sible steps between a true female and 

 a true male. 



Mention of some intersexes already 

 existed in nematode literature ; there 

 were several short accounts of them 



in some species of Merniithidae, and a 

 description of those reported in other 

 genera is given in later paragraphs of 

 this paper. 



Unfortunately my experiments did 

 not have the desired results. It seems 

 to be very difficult to cross the sj^ecies 

 of the genera mentioned in the foot 

 note. Thus far my experience agrees 

 with that of Maupas, published in a 

 posthumus paper edited by Caullery." 



During the last few months the 

 writer was called upon to identify a 

 large number of Mermithidae. Nu- 

 merous intersexes were observed. Since 

 the sex problem is today a center of 

 biological discussion, a description of 

 these intersexes is certainly of some 

 interest at this time. 



Intersexes in the Hair-Worm 



Hitherto every investigator who has 

 studied any considerable number of 

 Ag. albican/' or related forms, men- 

 tions the presence of intersexes' in this 

 species. Meissner in his splendid 

 studv of this form describes as early 



^ For the opportunity to carry on these experiments I am greatly indebted to the authori- 

 ties of Yale University and the staff of the Osborn Zoological Laboratory, New Haven, Conn. 

 Species of Rhabditis, Plectus, Cephalobus and Diplogaster were used in these experiments, 

 an account of which will be given in a later paper. 



" Maupas, Emile, Essav d'Hvbridation chez des Nematodes. Bull. Biol, de la France et 

 de la Belgique. T. 52. 1919. 



■' During recent experiments it was found best to split the former genus Mermis into 

 several new genera. In the future the genus Mermis will include only those forms with 

 four head papillae, two mouth papillae, amphids situated laterally in the same level with the 

 head papillae, mouth terminal, vagina S-shaped ; type species M. nigrcscciis Ditj. The new 

 genus Agamcrmis will include forms with six head papillae, no mouth papillae, amphids 

 mostly behind the lateral head papillae, or slightly shifted dorsad, mouth terminal, vagina 

 S-shaped. In entering the host the preparasitic larva of this genus drops five-sixths of its 

 body through self-amputation at a preformed node. Our type species, Ag. dccaudata resem- 

 bles very much the former Mermis albicans as described by Meissner and partly by Hagmeier, 

 but differs from it through the structure and position of the amphids or lateral organs, and 

 the cells around the esophagus. Furthermore it is not known whether in the latter form 

 the tailpart of the larval body is dropped by self-amputation, as in Ag. dccaudata. We are 

 sure that M. albicans of earlier investigators includes perhaps a number of different species. 

 For further details, see the preliminary paper: Cobb, Steiner, and Christie, Agamcrmis 

 dccaudata. a Nema Parasite of Grasshoppers and Other Insects. Journal of Agricultural 

 Research, Vol. 23, No. 11, 1923. 



* Thev were not termed such, but were called hermaphrodites or "Zwitter." 



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