Steiner: Intersexes in Nematodes 



157 



made before the matter will be cleared 

 up. From my own observations I be- 

 lieve that variations similar to those 

 described above for A(j. dccaudata and 

 related forms may be found in other 

 ^lermithid species. 



Exactly why the Alermithids produce 

 such an abundance of intersexes, is still 

 unknown, and also why. apparently, 

 only females show interssxual charac- 

 ters. Hitherto no one has observed, 

 or at any rate mentioned, intersexual 

 males in this family. In regard to Ag. 

 dccaudata it may, however, be men- 

 tioned that the number of the papillae 

 on the tail end of the male is extremely 

 variable, as is the arrangement also. It 

 is hard to find even two specimens 

 which are in this regard perfectly 

 alike ; also the length and even the 

 form of the tail itself is somewhat 

 variable as well as the length of the 

 spicula (Figure 10). 



Intersexes in Free-Living Nematodes 



Apart from the family of the ]\Ier- 

 mithidae intersexes have been seen in 

 very few other nematode genera. Some- 

 what outstanding in this regard is the 

 genus Trilobits, including a number of 

 fresh-water free-living forms. In 1905 

 (1. c. p. 55) E. von Daday describes 

 a very pronounced case of intersexuali- 

 ty in Trilobits loiigiis Leidy (Trilobus 

 dk'crsi-papillatus v. Daday.) It was 

 an intersexual female. The ovaries, 

 uteri and vagina of this female were 

 well and normally developed, the vulva 

 had its normal position and eggs were 

 seen within the uteri. But this female 

 had also well developed spicula, and. 

 according to v. Daday. all the preanal 

 accessory organs of the male, consist- 

 ing of a group of three large, three 

 medium-sized and numerous small pre- 

 anal papillae. He claims even to have 

 seen a short testis with a short ductus 

 cjaculatorius, but apparently not func- 

 tioning. 



]\Iore often intersexes have been 

 observed in Trilobus gracilis Bastian. 

 Of this species Ditlevsen mentions a fe- 

 male with well developed male papillae, 

 such as characterize the male, but with- 

 out spicula and gubernacula. Recentlv 



Wilhelm Schneider observed two inter- 

 sexual females of the same species. 

 One had completely developed spicula 

 but no trace of any papillae, the other 

 female showed only three preanal pa- 

 l)illae. whereas the spicula apparently 

 were absent. Both specimens had well 

 developed female organs. Dr. N. A. 

 Cobb tells me that he also has observed 

 on several occasions intersexual females 

 in Trilobus at Washington. D. C. and 

 Mr. Thorne tells me the same thing 

 for specimens living in fresh water 

 from Utah. 



Regarding the causes of the intersex- 

 uality in this group of free-living 

 nemas. it is of interest that, at least in 

 Trilobus gracilis Bastian, there exist a 

 series of races, genotypes or varieties 

 already mentioned by several authors. 

 I refer in this regard to the paper of 

 Stefanski (1917). and one published bv 

 the writer (Steiner, 1919). Undoubt- 

 edly we have here a whole series of 

 closely related, but slightly different 

 forms, probably not all known. Here, 

 too, tlie observed intersexes rnav 

 be related zvith hybridization betzvecn 

 these different genotypes. The above- 

 mentioned Trilobus longus is regarded 

 by Micoletzky (1921) as only a variety 

 of T. gracilis, but further studies have 

 yet to prove the correctness of this con- 

 ception. 



Intersexes in Marine Free-Living 

 Nemas 



J. G. de Man mentioned in 1893 a 

 thoroughly functional female of Thor- 

 acostoma figuratum Bast, with the spic- 

 ula, and the gubernaculum of a male 

 and a similar specimen of a female of 

 Chronuidora poecilosonia de ^lan. 



In 1904 the same author mentions 

 another very interesting case. Of nine 

 s|)ecimens of Enoplus inichaelseni v. 

 Linst. found in algae growing on Gas- 

 teropods in the Bay du Torrent, Isle 

 of Londonderry, Canal francais. An- 

 tarctic, he observed three females (they 

 were the largest in size ) . with very pro- 

 nounced intersexual characters. Two 

 of them had eggs in the uteri ; all three 

 had the preanal. ventro-medial cutinized 

 gland outlet of the male and also a 



