11 
in English, and altogether there is very little upon the group readily 
I I available to the American physician. In the preparation of this paper, 
I i practically the entire literature of Ilymenolepis in man has been con- 
sulted, with the intention- of bringing together everything that is 
known to date, regarding this genus in its relation to human medicine. 
j Genus H YMENOLEPIS « Weinland, 1868. 
Generic diagnosis. — Family Tseniidse, subfamily Dipy lidiinie : Head generally 
j small; rostellum retractile, well developed and armed, or rudimentary and unarmed; 
suckers usually unarmed. Genital pores, single, marginal, unilateral. Testes few; 
usually three in each segment. Uterus sac-like; often filling the segment; frequently 
. with outpocketings and incomplete partitions. Eggs with two, three or four mem- 
!• branes, the inner of which closely invests the embryo and may exhibit a small 
' mamillate projection at each pole; the outer membrane is separated from the inner 
i|. by a wide intervening space. Larva a cercocyst or staphylocyst. 
III ; . Type species. — Ilymenolepis flavopunctata 'W einlajid, 1858 =LT. diminuta (Rudolphi, 
I A819). 
The genus Hymenolepis was established by Weinland in 1858 with 
H. flavopunctata (= H. dmiinuta) as type, but was neglected almost 
|i entirel}^ until rehabilitated by Blanchard in 1891. The characters of 
the genus as it now stands cover 30 or 10 species, some of which in 
I many respects are widely divergent. It is therefore likely that in the 
! course of time some of these species will be taken out of the genus and 
' placed in new genera. Cohn (1899 c, e, g, 1900 b, 1901 b) has recentl}" 
taken a step in this direction by proposing a division of the genus 
into two subgenera. In the subgenus Hyinenolepis he would place 
those forms of the group which possess either an unarmed and rudi- 
mentary rostellum, or a rostellum armed with 20 to 30 hooks. In the 
second subgenus Drepanidotdenia\iQ would place forms possessing 8 to 
10 hooks. According to this classification, II. diminuta and II. noma 
fall together in the first subgenus, and II. lanceolata in the second. 
There are, however, certain objections to this scheme of classification, 
one being that it is decided!}^ artificial and as such has been opposed 
b}" AVolffhugel (1899b, 1900 b) and also by myself in a former paper 
(Ransom, 1902). As an indication of the artificial nature of the proposed 
classification, it ma}" be remarked that there are, in the group, tape- 
worms with 8 to 10 hooks which resemble, in the greater part of their 
anatom}", worms with rudimentary rostellum much more than they 
resemble other worms with 8 to 10 hooks; consequenth", the use of a 
character, based upon the number of hooks, as a criterion in classifi- 
cation would often result in placing in one subgenus a species which, 
in all essentials except this one character, resembled the species typical 
of the second subgenus, more than it resembled the type of the first, 
and vice versa. 
« Synonyms. — Hymenolepis Weinland, 1858; Diplacanthus AVeinland, 1858 (not 
Agassiz, 1842, fish); Lepidotrias Weinland, 1858; Ilymenoleps is of Osier, 1895, and 
other authors (misprint); Diplacanthus of Cohn, 1899 (misprint). 
