SUBGENUS MONONCHUS 



(S. s.461) 159 



equal to the length of the tail, the posterior member of the series being a short 

 distance in front of the anus. There are 3 pairs of somewhat equidistant subven- 

 tral post-anal papillae on the anterior part of the tail. There are also lateral 

 papillae on the tail. 



This beautiful, ac- ^ ^ 6 *| '& *|^ 2- M ^-7^-7-^^ _ ^ 



tive, rather common 2 6 ? 25 M 92 

 species is found in ? ? ^ ? T~~^ ll8 BB 

 the soils of meadows and marshes in many parts of 

 Europe ; it is also aquatic. The writer has followed 

 Dr. de Man's rehabilitation of Bastian's macrostoma. 

 Corresponding females which the writer has found at 

 the Arlington Farm, Virginia, U. S. A., indicate the 

 presence of exceedingly fine transverse striae, and of in- 

 conspicuous wings. Amphids obscure, just behind the 

 lips, difficult to see except in dorso-ventral view. The 

 oesophagus receives the basal fourth of the pharynx, 

 and in this region is very slightly swollen. The writer 

 failed to see the minute basal onchi mentioned by de Man. The thin-shelled eggs, 

 which occur in the uteri one at a time, are about one and one-fourth times as long 

 as the body is wide and about half as wide as long, and are apparently deposited 

 before segmentation begins. The writer has no doubt this species is syngonic. A 

 female which had yet to undergo the final moult contained an egg which had its 

 shell completely formed, and was evidently in a state preparatory to segmentation. 

 Flemming solution to glycerine. Fig. 28 (after de Man). 



According to Bastian -the following differences exist between macrostoma and 

 truncatus; macrostoma is 50 per cent longer, and is relatively narrower in the ratio 

 of 3.5 to 5.3. Macrostoma tapers less in the neck, and has papillae, while truncatus 

 has none. While macrostoma is the larger, its pharynx is no longer ; the onchus is 

 a little farther forward. The intestine in macrostoma is less distinctly tessellated. 

 The posterior part of the oesophagus in macrostoma is figured as having an internal 

 expansion. These characters seem to the writer sufficient to separate the two 

 species. It is probable that papillae on the head of truncatus were overlooked by 

 Bastian. This would have been easy, for instance, if the papillae on truncatus are 

 similar to those on megalaimus. See figure 27. 



16. M. obtusus, n. sp. Papillae setose. The adjacent figure (29) is after 

 2.4 > 25. ^50+^ 87. Biitschli, whose 



275 ? 472 ? 3.3 1-7 " figures seem to 

 represent a different species from that figured by de 

 Man under the name macrostoma, notwithstanding the 

 general resemblances. The proportions of the tail and 

 of the spicula are different in the two forms; the dis- 

 tribution of the papillae on the tail is also different, and, 

 while the number and position of the pre-anal ventral 

 supplementary organs are about the same, their form as 

 shown by Biitschli is decidedly different from that 

 shown by de Man. In addition, Biitschli's figure shows 

 3 pairs of pre-anal, ventrally submedian papillae coex- 

 tensive with the ventral row. Biitschli's data may there- 

 fore, the writer thinks, be taken as establishing this new 

 species. Synonym, M. truncatus Bastian of Biitschli. 

 Found in the River Main, Germany ; common in mud 

 and in aquaria and among aquatic plants, in moving water not foul. See also fig. 15. 



