2 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



that some of the specimens referred by him to Distomum ocreatum do 

 not belong to this species. 



My studies have been made on specimens taken from the stomacli of 

 both Anguilla chrysypa Raf.^ and Osmerus mordax Mitchill during the 

 mouths of October and November. The parasite is by no means com- 

 mon, as I have frequently examined fifty or more stomaclis without finding 

 a single specimen. When present, the number found in a single host 

 varied from one to fifteen or twenty. In December I obtained very 

 few specimens, and after that did not succeed in finding any, althougli I 

 repeatedly examined stomachs of the infected species until about the 

 middle of May. 



Hot corrosive sublimate was found to give the best results as a fixing 

 agent for specimens to be sectioned, tiiough it was not at all satisfactory 

 as a fixative for specimens to be mounted entire. For the latter purpose 

 Kleinenberg's picro-sulphuric mixture gaveT the best results. Alum 

 carmine and Brazilin proved most satisfactory for staining sections and 

 Delafield's haematoxylin for entire preparations. The work has been 

 carried on under the direction of Professor Mark, to whom I am indebted 

 for many suggestions and much valuable assistance. 



External Characters. 



Upon measuring seven preserved specimens with the appendix extended 

 (compare Fig. 1), it was found that the average length was 2.6 mm., the 

 extremes being 1.71 mm. and 3.219 mm. The average width was 

 0.323 mm., the extremes being 0.222 mm. and 0.444 mm. Tiie average 

 length of the trunk was 1.982 mm. and that of the appendix 0.799 mm., 

 the appendix being therefore a little more than three-eigliths as long as 

 the trunk. Llihe (: 01) states that the appendix reaches about three- 

 fourths the length of the trunk. 



The ventral and oral suckers are very nearly equal in size. From 

 measurements made on five specimens, it was found that the average 

 diameter of the oral sucker was 0.224 mm., while that of the ventral 

 sucker was 0.2G46 mm., though in some cases the oral sucker is equal 

 in size to the ventral or even a little larger. The oral sucker is at the 

 anterior end and faces antero-ventrally. From measurements on the five 

 specimens, it was found that the distance of the centre of the ventral 

 sucker from the anterior end of the body was from one-fourth to one- 

 seventh of the entire length of the worm. The genital pore lies ventral 



1 Rafinesque ('17) spelled this name chrisypa. 



