W. Nicoll 
335 
Genus iv. Helicometra Odhner 1902. 
To this genus five species have now been referred, viz. H. pulchella 
(Rud.), II. fasciata (Rud.), II. sinuata (Rud.) II. mutabilis (Stossich 
1902) and II. flava (Stossich 1903). Two other species described by 
Stossich, namely Distomum gobii aud D. labri, also belong to this 
genus, but the latter was found by Odhner (1902) to be identical 
with H. pulchella. The identity of all the species, however, can 
hardly be regarded as beyond question. The genus Helicometra as 
defined by Odhner (1902, p. 161) forms a distinct systematic unit, 
the outstanding feature of which, separating it from all other Allo- 
creadiinae, is the filamented condition of the ova. At the same 
time it is unfortunate that the genus should have been founded on 
a type-species which is, strictly speaking, still a species inquirenda, 
for Odhner failed to elucidate the anatomy of Distomum pulchellum 
Rud. on a point which may prove to be of the greatest importance, 
namely the condition of the testes. Odhner’s identification (1902, 
p. 160, note 2) as the type specimens of Distomum pulchellum Rud. 
certain specimens in the Berlin collection labelled “ Distomum Sp. 
Labrus cynaedus Neapel. Coll. Rudolphi” is itself open to dispute, 
although the probabilities are very much in its favour. Still more 
questionable is his conclusion that Distomum labri Stossich (1887) is 
identical with the form which he describes as H. pulchella (Rud.). It 
is almost inconceivable that Stossich could have described the testes as 
multilobate, with five to six lobes, had such not been the case. Yet 
Odhner examined one or more of Stossich’s specimens and found them 
to agree with his own, in which the testes are entire ( ganzrandig ), the 
statement of which fact being underlined. It is evident that some 
discrepancy has entered here, the significance of which Odhner either 
ignored or failed to grasp. A possible explanation will be offered in the 
following notes. 
By the kindness of Professor Monticelli of Naples, specimens of 
Distomum gobii (from Gobius jozo ) and Helicometra mutabilis (from An¬ 
guilla vulgaris) from Stossich’s collection were placed at my disposal. 
Specimens of Distomum labri and Helicometra flava were not available. 
From an examination of this material I have not the slightest doubt 
that the first two species are identical with each other and with the 
form which I am describing here as Helicometra pulchella. Distomum 
labri is also certainly identical with these and there is more than a 
