VOLUME 16 ,JULY, 1949 NUMBER PROCEEDINGS of The Helminthological Society of Washington Supported in part by the Brayton H . Ransom Memorial Trust Fund EDITORIAL COMMITTEE EDWARD G. REINHARD, Editor The Catholic University of America EMMETT W. PRICE U. S. Bureau of Animal Industry GILBERT F. OTTO Johns Hopkins University WILLARD H. WRIGHT National Institutes of Health GOTTHOLD STEINER U. S. Bureau of Plant Industry, Soils, and Agricultural Engineering Subscription $1 .75 a Volume ; Foreign, $2.00 Published by THE HELMINTHOLOGICAL SOCIETY OF WASHINGTON THE HELMINTHOLOGICAL SOCIETY OF WASHINGTON The Helminthological Society of Washington meets monthly from October to May for the presentation and discussion of papers . Persons .interested in any branch of parasitology or related science are invited to attend the meetings and participate in the programs and are eligible for membership . 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Com- plete sets from 1934 through 1948 are available at $1 .00 a volume (domestic U .S .A .) or $1 .25 (foreign) except volumes 1 and 2 which are $3 .00 each (domestic) or $3 .50 (foreign) . Remittances should be made payable to The Helminthological Society of Wash- ington and sent to the corresponding secretary-treasurer . Correspondence may be addressed to the corresponding secretary-treasurer, Edna M . Buhrer, Division of Nematology, Plant Industry Station, Beltsville, Md ., or to the editor, Edward G . Reinhard, Department of Biology, Catholic University of America, Washington 17 . D . C . PROCEEDINGS OF THE HELMINTHOLOGICAL SOCIETY OF WASHINGTON VOLUME 16 JULY, 1949 NUMBER 2 On the Classification of the Tylenchida, new order (Nematoda, Phasmidia) GERALD THORNE U. S . Bureau of Plant Industry, Soils and Agricultural Engineering, Salt Lake City, Utah The nemas commonly known as ''tylenchs'' have heretofore been assigned to the Order RHABDITIDA which includes those phasmidians possessing an esophagus which is divided into corpus, isthmus and bulbar regions . This classification brought together such divergent groups as the tylenchs, cephalobs and rhabditids which, in many respects, are vastly different from one another . To one who has observed many thousands of specimens of RHABDITIDA, it has long been evident that the tylenchs are very remotely related to the other groups . There are certain differences in their general and detailed morphology which have been inadequately evaluated in formulating their taxonomy, and too much attention has been given to finding minor similarities and overemphasizing their importance . True, there may have been a common ancestry in remote antiquity but the lines through which the various groups developed have been separated so long that but little semblance remains. Actions and habits of tylenchs readily separate them from other forms, and one well acquainted with the various groups should easily distinguish them by these points alone . Reactions to stains are most revealing and it generally is a simple matter to separate the tylenchs in a mixed collection by the particular tints of color which they exhibit, showing that their body tissues have distinctive qualities . The classification here outlined is based upon more than 6,000 specimens representing almost 200 species from 28 genera of Tylenchoidea which have been assembled in the Division of Nematology collection at Salt Lake City, Utah, during the past 30 years. Collections have come in from 24 states, Alaska, and the Hawaiian Islands, with the greatest numbers from Utah, California, Nevada, Idaho and Colorado. Canada, Australia, England, Netherlands, Germany and 11 other foreign countries are represented . But even this wealth of material has many limitations and the outline presented doubtless will be found inadequate within a few decades, because probably not more than 20% of the genera and 5% of the species have been discovered and future workers will be forced to make some alter- ations and many additions . Suborders and additional superfamilies doubtless will be established as the group is expanded by global collecting . Let us hope that changes will be made on specimens actually in hand and not on theory . The task will not be one for the over-enthusiastic neophyte with just a few collections, but rather one for the experienced hematologist with thousands of specimens on which to base extremely careful work . The illustrations accompanying the following diagnoses have been prepared just as carefully as was possible . Face views showing arrangements of the amphid apertures and cephalic papillae are necessarily somewhat schematic and frequently 37 the prominence of these minute organs is exaggerated . Observations have been made through a 1 .5 mm oil immersion objective and 5X and 10X oculars, from which all side lights have been eliminated by means of a heavy cloth screen fitted about the ocular . An observer working at an open table with side lights interfer- ing with his vision would find it impossible to see many of the details shown in these face views . With equipment superior to that used by the writer and excep- tionally good eyesight, someone may eventually locate and illustrate the cephalic papillae, deirids and phasmids which the writer has been unable to see on certain species. Improved staining techniques are especially desirable for this critical type of work and future workers should investigate their possibilities . Generally observations have been made on specimens killed by gradual heat, fixed in formalin-alcohol-acetic acid solution and mounted in glycerin, although some specimens have been observed before killing and fixing while others were stained and mounted in balsam . Face views and cross sections were prepared by cutting off the desired portions with a very slender eye knife and mounting in hard glycerin jelly, a comparatively simple process when once one has mastered the technique. The purposes of this paper are threefold : 1 . To establish the order TYLENCHIDA and outline the general relationships of the free-living and plant parasitic nemas belonging in the superfamily Tylenchoidea . 2. To emend the diagnoses of some of the more common genera of Tylenchoidea . 3. To add new information on the morphology of tylenchs, especially those characters which have been found to be of value in making generic and specific diagnoses . In the descriptions of species the ratios given are a combination of those used by de Man and Cobb . For a, (3, and y we have -substituted a, b, c . These are the ratios, respectively, of body length to body diameter, to length at base of esophagus and to tail length . " V" is the position of the vulva as a percent of body length ; superior figures indicate extent of ovary or uterus from vulva as a percent of body length . "T"T" is the extent of the male gonad anteriad from the anus . No attempt has been made to cover the families and genera of Aphelenchoidea (Fuchs 1937) . Likewise the Tylenchoidea parasites and associates of insects under the families Myenchidae, Pereira, 1931, and Allantonematidae Chitwood and Chit- wood, 1937, have been omitted . Order TYLENCHIDA, new order Diagnosis.-Nematoda, Phasmidia . Stoma armed with a protrusile spear or stylet (except degenerate males of a few species) .