94 
ments this striation is not apparent, and the membrane is much thinner. 
In still younger segments the eggs are considerabh^ smaller and the 
shape is commonly oval. 
A number of authors give the sizes of the eggs as follows: 
Dujardin (1845a, p. 579): Outer envelope, 62 to 74/^; inner envel- 
ope, 41 to 42 //; embryo, 32 to 36 yw; hooks, 15 to 17 yw. 
Weinland (1858, p. 55): Outer envelope, 54 yw; embryo, 24 yw. 
Leuckart (1886a, pj3. 661-663, from Weinland’s material): Outer 
envelope, 60 embryo, 30 yw; hooks, 17 yw. 
E. Parona (1884): Outer envelope, 58 to 68 yw. 
Grass! (18881): Outer envelope, 70 to 86 yw; embryo, 36 by 28 yw; 
hooks, 11 yw. 
Zschokke (1889), no measurements given. 
Leidy (1884a, p. 110): Outer envelope, 72 yw; a few oval eggs 80 by 
72 yw; embryos, 40 by 32 ju. 
Magalhaes (1896): Outer envelope, about 59.5 yw; embryo, about 
34 yu. 
Sonsino (Sonsino & Zschokke, 1896): Outer envelope, 75 yw and 80 
by 75 yw; hooks, 14 yw. 
In measurements which I have made of eggs of specimens, both 
from the rat and from man (Leidy’s material), the outer envelope 
ranged, in both cases, from 64 to 80 yw; the inner, 24 by 20 yu to 36 by 
28 yw; the hooks, 14 to 16 yw. 
The middle pair of hooks differed from the other two pairs in the 
same manner as mentioned above in connection with II. nana^ namely, 
they were more delicate and the ventral root was onh" very slightly 
developed. 
Besides the eggs of ordinary size it is not uncommon to find in 
mature segments now and then an egg considerably smaller, round or 
slightly oval, wdth the outer envelope much thicker than is usual in 
the larger eggs. Four such specimens gaA^e sizes ranging from 40 by 
40 yw to 40 bv 48 /u 
Sonsino (Sonsino A Zschokke, 1896, p. 939) has found that the ova 
will remain alive in water at least fifteen days. 
DEVELOPMENT AND LIFE HISTORY. 
It is to the observations of Grassi & Rovelli (1888b, 1889a, 1889b, 
1892a) that we owe our knowledge of the life history of Ilymenolepis 
diminuta. Their results (as given in Grassi & Rovelli, 1892a, pp. 
31-33, 90-92) are as follows: 
All attempts at direct infestation resulted negatively. 
The cysticercoids were first found in the larva of the meal moth and 
its adult {Asoynci farincdis)^ then in }mung and adult earwigs {Anisola- 
Ms annidijyes Lucas), and finally in adults of beetles {Acis spinosa 
(Linnseus) and Sccairus striatm (Fabricius). They live in the abdom- 
