408 RTT.T.ETIX OF THK T'^'TTED STATK:^ FISH COMMT^SSION. 



tho siil)j(Tl-iii;itt('i- imdtT the scvi-nil liosts lias i^ivatlv fai'ililatfd tlii> j)laii. In all 

 cases, whi'iv not ('Xi)licitly sbitpd to ho otherwise. tln> food notes state the food as it 

 was aetually found in the Woods Hole fishes. 



Analytical keys for the determination of frenera of cestodes and sjiecies ol 

 distoines mentioned in this paper have hoen introduced. For the determination of 

 monogenetic tiematodes recour.se may be had to Pratt's Synopsis of the Hetorocotyleu 

 (.\miTican Naturalist, vol. xxxiv. pp. <i4.">-titi-2|. 



Hut few changes have been made in the nouK'nclaturc adopted in former papers, 

 althoujjfh this is not because the author is entirely satisfied with the old. The ccst-ode 

 oi-iirinally called (>ry<iiiiiit(>f>ofhriuin Ktu/u.-itiiiii has been I'cfcrrcd in this ])aper to 

 tlie '•enus < 'rnxxuhothrluiii. Following the nomenclature of I'l'att's excellent .synopsi.s, 

 OctdhothrJutii denticidatuiii becomes Dactylot-otyle deiiticulatum,, Octnplectamun wfjine 

 becomes PirHdiijihniu njfinlx, jVltsxcJiiii ihyaiix hcconics .\. ihinijiifii . and I riiftotiium, 

 riiiliiljihiiinitiii becomes 7'. liioke. 



The generic name Plutinmiui is ret4iine<l. as it i-^ ^uliiiirntly dclinilc for tlie 

 puj'poses of this paper, nurinjr th(> past summer the aullioi- has been nuich 

 impressed by the \ariety of sliupcs which the same -;pecics of <listoine may assume, 

 even when il i> undi'i' the same conditions. W Ihmi \arialiipiis in conditions arc niailc. 

 as. for example, when some are placed in fresh water, otliers in sea water, others in 

 normal salt solution, or when tiiev ar(> killed under pressure with application of 

 heat, or when ditlcreiit killing fluids are used: further. \\ lii'U ditl'erences in age of 

 sjiecimens are considered, as ati'ecting the occui'reiu-e of spines on the body orai'oiuid 

 the mouth, or the relati\e proimrtions and evi'ii disposition of the reproductive 

 organs, the \aricty nl' I'ornis In lie found in the same species is vei'v gieat. The 

 vai'iation in proportions of the uuiscular suckers. e\('n. is often considciable among 

 the individuals of the same species, and the ova. while furnishing a \aluable criterion 

 of species, freijuentiy vai'y in the same .species and even in the same individual. 



The explanation of the wide distribution of such a form as tiu' species idenlilied as 

 Dixtiiiiiniii iij>j>iii<li<iiliitiiiii is doubtless to be found in the nature of the intermediate 

 host or hosts. Pratt' describes an immature a])pendiculate distome which he finds 

 in copepods. which, without much doul)t. is the young of this s])ecies. Since copepods 

 furnish tiie principal food of the majority of the young of the food-fishes, it is e:i,sy 

 to underst^md how the latter beeaiue infected. It is to be noted further that most of 

 tiie lish in which this distoiue was found w(>re young. 



While this i-e])()rt concerns itsi^lf principally with helminth entozoa. a few 

 ectoparasites, both lirlmintlis ;ind copepods. and a few sporozoa are noted. Some 

 deep-water tishes are included which do not lu'long to the Woods Hole faima. 



Notes on the nematodes, which have been collected by or for the author at 

 Woods Hole, are given, together with notes on nematodes which were found in a 

 collection of entozoa l)elonging to the Initcfl States National Museum, the cestodes 

 and trematodes of which were reported on in vols, xix and x.\ of the Proceedings 

 of the NatioiKil Mu-cum (Nos. 4, 5, and O. j). 4i'4). The great majority of these 

 nematodes are innnatun' and no attempt has licen made to gi\'e them specitic names. 

 A few adult forms, with suthcieiitly conspicuous characteristics, have been described 

 as new .species. These will be found in the alphabetic list of nematodes (p. 410-411). 



>A Contribiition to tbi' Lifc-hi.slory unci Anuloniy nf the Appendiculate Distomcs, Zoolog. Jabrb. XI, 1898. 



