131] LIFE HISTORY OF GORDIUS AND PARAGORDIUS—MA Y 11 



Several adults of this species were collected early in June of 1914. 

 Hundreds of specimens were obtained at Douglas Lake, Michigan, during 

 June, July and August, 1915, and a few more at Urbana in the spring of 

 1916, Material from the collections mentioned under Gordius robustus 

 was also available. 



Eggs and larvae were obtained in large numbers wherever adults were 

 found. 



Parasitic stages were obtained in the fall of 1914 from one host given 

 to me by Minnie Watson Kamm, who was working on gregarines in this 

 laboratory at that time. Abundant material was obtained in all but the 

 very youngest stages in the summer of 1915 at Douglas Lake. Over 500 

 specimens were available for study. 



The ordinary methods used in anatomical and histological study were 

 found to be almost useless when applied to the study of the Gordiacea and 

 special methods had to be adapted and devised at nearly all stages of the 

 investigations. 



The study of living material was confined mostly to field observations 

 on adults and hosts and to the study of the embryonic development and 

 larval structure. Nothing is gained by the study of the parasitic forms in 

 the living condition. 



For the removal of parasites from the hosts it was necessary to use a 

 normal salt solution of full strength (0.75%). Even in this a slight injury 

 usually caused a flowing out of part of the body contents. In pure water 

 the specimens rupture at short intervals all along the body almost as soon 

 as immersed. This applies of course only to the younger stages and not 

 to those that have already formed the adult cuticula. The specimens were 

 usually removed by tearing away the host tissues in salt solution by means 

 of fine forceps or needles. For smaller specimens the host tissues were 

 teased out in a watch glass and the contents examined under the low 

 power of a microscope at a magnification of about 100 diameters. 



The problem of the proper killing fluid was one of the most difl&cult to 

 solve, and in part has not yet been solved. On account of the special 

 methods of dehydration and imbedding it was impossible to test out quickly 

 the action of any particular killing fluid and on account of the short seasons 

 at which material was available such testing could usually not be done 

 during the collecting season. It was necessary under those conditions to 

 use the rapidity with which the killing fluid acts and the general appearance 

 of the killed material as criteria. Most of the earlier material was killed in 

 a saturated solution of corrosive sublimate to which from five to ten per 

 cent of glacial acetic acid had been added. Later this solution was saturat- 

 ed with picric acid because with that modification it killed specimens more 

 quickly and prevented to a great extent the rupturing of the parasitic 

 forms in the killing fluid. But histological preparations show that this 



