68 PROCEEDINGS OF THE NATIONAL MUSEUM vol.88 



P. olssoni lias a tendency, especially if placed in fresh water or 

 weak formalin, to become turgid, in which case the neck is reflected, 

 often until it stands at right angles with the body. The ovary in 

 both species is lobed, usually somewhat pestlelike with three lobes at 

 the posterior end. 



Distomes from a large number of Woods Hole fishes are here re- 

 corded. While showing much variation in shape and proportions, 

 and in minor details of structure they agree in essential particulars 

 with Odhner's description of the species. 



Hosts. — ^Long-spined sculpin {Acanthocottus octodecimspinosus) , 

 American sole {Achirus fasciatus), sand launce {Ammodytes ameri- 

 canus), American eel {Anguilla rostrata)^ lumpfish {Gyclo'pterus 

 lumpus)^ common codfish {Gadus morrhua)^ common eastern stickle- 

 back {Gladiunculus hispinosus), sea raven {Hemitripterus ameri- 

 camis), conger eel {Conger conger)^ tomcod {Microgadus tomcod)^ 

 white perch (Morone americana), grubby (Acanthocottus aeneus), 

 American, smelt {Osmerus mordax)^ summer flounder {Pardlichthys 

 dentatus)^ yellow perch {Perca flavescens), codling {Urophycis 

 chuss), pollack {PoUachius virejis), common gurnard {Mendinus 

 carolinus), puffer {Sphoeroides mactdatus), goggler (Trachuoops 

 crumenophthalma) , garfish {Strongylura marina). 



Record of collections- — Collected by Vinal N. Edwards from the 

 sculpin on 17 dates in 6 different years in the months of February, 

 March, April, May, October, November, and December. (U.S.N.M. 

 No. 8230.) The largest number recorded on any date was 19, when 

 8 fishes were examined; lengths, in formalin from 1.4 to 6 mm. 

 The vitellaria in these distomes from the sculpin are, as a rule, inter- 

 rupted at the level of the testes. Two were noted in which the vitel- 

 laria were continuous. On a slide containing 10 distomes, 5 were 

 noted with vitelline follicles in front of the ventral sucker. Of some 

 30 other mounted specimens only 2 had the vitellaria as far forward 

 as the anterior border of the ventral sucker. In a small proportion 

 of the mounted specimens the testes are slightly lobed. Measure- 

 ments in balsam : Length, 4.83 mm., breadth, 0.77 mm. ; oral sucker, 

 length, 0.18 mm., breadth, 0.23 mm.; pharynx, length, 0.11 mm., 

 breadth, 0.11 mm.; ventral sucker, length, 0.34 mm., breadth, 0.38 

 mm.; first testis, length, 0.42 mm., breadth, 0.35 mm.; second testis, 

 length, 0.42 mm., breadth, 0.42 mm. ; ova, 0.072 by 0.042 mm. 



From American sole: One, immature, collected October 14, 1915. 

 Measurements in balsam : Length, 1.09 mm., breadth, 0.29 mm. ; oral 

 sucker, length, 0.08 mm., breadth, 0.11 mm.; pharynx, length, 0.045 

 mm., breadth, 0.03 mm.; diameter of ventral sucker, 0.18 mm.; 

 breadth of first testis, 0.14 mm. 



From sand launce: Two (U.S.N.M. No. 8231), collected Octo- 

 ber 14, 1914. Length, in formalin, 4 mm. Twelve fish examined. 



