108 
widely separated from the outer membrane. There is thus consider- 
able similarity between the eggs of Hymeiiolepis laaceoJata and H. 
diminuta. The outer membrane of the former, however, does not 
become thickened as in the case of the latter, but remains very thin, 
and the intervening substance between the two membranes is less con- 
spicuous and does not ordinarily present the appearance of a third 
membrane as is usual in the latter instance. The inner membrane 
occasionally presents polar papilla? as in II. diminuta and II. luina. 
The egg measures, according to Railliet (1893). 50 by 35 /^, and the 
embryonal hooks, according to Krabbe (1869), 8 y. According to my 
own measurements the outer membrane varies from 60 to 100 y in 
diameter, the inner measures 30 by 25 y to dO by 25 yw, and the hooks 
from 12 to lb y. 
DEVELOPMENT AND LIFE HISTORY. 
Mrazek (1896, p. 11) mentions some cysticercoids which he found in 
various small crustaceans of the family Cyclopida?. These cysticer- 
coids agreed as to the form and size of the hooks with II. Imceolata., 
and ^Irazek accordingly considered them the intermediate stage of the 
tapeworm under discussion. He gives no description or ligures, 
merely remarking that the cysticercoids are almost exactly similar to 
those of Teenia set Ig era. 
Dadai (1900a) found a large number of specimens of a cercocystis 
(tigs. 126-130) in small Crustacea. Dlaptornas sjyino-sus Dadai. collected 
from stagnant pools in Yadkert. Hungary, which he would identify 
with Ilyrnenolepjls {Drepanidotsenia) lanceolata (Bloch). 
The cyst is more or less spherical with a remarkably thick wall, the 
circidar and longitudinal muscle layers being remarkably well devel- 
oped. A few calcareous corpuscles were seen in the inner layer of 
the parenchyma of the cy^^t wall. The cyst measured 0.23 to 0.2S 
mm. in length, and U.18 to 0.23 mm. in diameter. 
The head was occasionally seen extruded through the anterior open- 
ing of the cyst (hg. 128), but usually was found retracted and tilling 
the cavity of the cyst almost entirely (tigs. 126. 127). The rostellum 
was either retracted into the scolex or protruded. The number (8) 
and the form of the hooks (tig. 127) was the same as in II. lanceolata., 
but their size was very different, 55 to 60 g. while in the latter they 
measure only 31 to 35 /l which renders the correctness of Dadai's 
identification rather doubtful. 
The caudal appendage is remarkable for its very great length. Its 
surface is very frequently marked by ring-like corrugations. It con- 
sists chieffy of granulated protoplasm and sometimes of masses of 
parenchyma cells; running lengthwise through its center is a char- 
acteristic thread-like structure, which consists of a dark, finely granu- 
lar laver of protoplasm surrounding a still darker central liber (tig.* 
127). ^ 
