11 
in English, and altogether there is very little upon the group readily 
available to the American ph 3 ^sician. In the preparation of this paper, 
practicalh" the entire literature of Hymenoleph in man has been con- 
sulted, with the intention of bringing together eveiything that is 
known to date, regarding this genus in its relation to human medicine. 
Genus H YMENOLEPIS « Weinland, 1858. 
Generic diagnosis. — Family Tseniidie, subfamily Dipylidiinae: Head generally 
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 
by a wide intervening space. Larva a cercocyst or staphylocyst. 
Type species. — Hymenolepis flavopunctata ^'' e \ Vi \ diiidi , 1858=LT. diminuta (Kudolphi, 
1819) . 
The genus Tlymenolepis was established b}^ Weinland in 1858 with 
H. Jlavopunctata (= AT. diminuta) as t^ye, but was neglected almost 
entirely until rehabilitated by Blanchard in 1891. The characters of 
the genus as it now stands coyer 30 or 10 species, some of which in 
many respects are widely divergent. It is therefore likeh’ 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 recently 
taken a step in this direction by proposing a division of the genus 
into two subgenera. In the subgenus Ilymenolepis he would place 
those forms of the group which possess either an unarmed and rudi- 
mentar}^ rostellum, or a rostellum armed with 20 to 30 hooks. In the 
second subgenus Drepanidot8enia\iQ would place forms possessing 8 to 
10 hooks. According to this classilication, IL diminuta and H. nana 
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 
by Wolffhugel (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 may be remarked that there are, in the group, tape- 
worms with 8 to 10 hooks which resemble, in the greater part of their 
anatomy, worms with rudimentary rostellum much more than they 
resemble other worms with 8 to 10 hooks; consequently, 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 3Ueinland, 1858; Diplacanthus AVeinland, 1858 (not 
Agassiz, 1842, fish); Lepidotrias Weinland, 1858; Hymenolepsis^’ of Osier, 1895, and 
other authors (misprint); Diplocanthiu'^ of Cohn, 1899 (misprint). 
