126 MR. F. J. MEGGITT ON A 
These were pipetted into a small watch-glass, water (pond or tap) 
was added, and they were examined every day for about two 
months. It was assumed that water would be the natural 
medium for their development, since under ordinary circum- 
stances they would be expelled into the pond and wait there 
until swallowed by their first host. Altogether 20 cultures 
were thus made and kept from the middle of October until the 
end of January, but with no results. The most advanced stage 
was that shown in Pl. ILI. fig. 23, but this was also observed in 
eggs taken freshly from a living specimen. Cultures were also 
made in salt solution, peptone, albumen, and fecal matter, 
different strengths being used, but with no result. 
While these cultures were going on, examples of the most 
common invertebrates in the reservoir (various species of Cyclops, 
Cypris, Nais, and Tubifex, together with some unidentified Ento- 
mostraca and numbers of aquatic insect larvee) were collected. They 
were placed in small dishes, each species being kept separately 
and in definite numbers. A certain amount of Diatoms, Huglene, 
Algee, etc., was placed in each dish for food, together with a large 
quantity of eggs. No results were obtained until Jan. 7th, when, 
after examining a Cyclops, the cover-glass accidently crushed it ; 
on re-examining it, several tapeworm eggs were seen in the 
crushed-out body-mass. All the cultures were then, and for 
some days afterwards, minutely re-examined, but eggs were only 
seen in the Cyclops. 
A fresh series of cultures was made with Cyclops from three 
localities to test this result, with a control to each culture. As 
was expected, the controls only gave negative results. The other 
cultures turned out better than was expected (see Table C): as 
many as 17 out of 20 Cyclops in one case were infected, while 
tliere were some infected Cyclops in every culture. The figures 
do not represent the whole truth, however. It is extremely 
difficult to keep the Cyclops alive under these artificial con- 
ditions; in one culture 4 out of 15 died in one week, in 
another 2 out of 6, in another 3 out of 7, ete. 
Schneider (22) found that in his infection experiments, feeding 
Gammarus locusta with eggs of a species of Proteocephalus, the 
Gammarus died in large numbers owing to too heavy infection: 
this may account for the death of some of the Cyclops, since as 
many as six larvee in one specimen have often been seen. As 
it is impossible to distinguish onchospheres in dead Cyclops, 
those dead cannot be counted. (In parenthesis, it may be said 
that the eggs appear to secrete a toxin which acts injuriously on 
other animals in the small culture dishes, but which, in the large 
volume of water in the reservoir, would be diluted until it would 
become negligible. In one instance a culture was started in a 
dish containing 20 Cypris, some Huglene for food, and some 
of the Cestode eggs; a control of the same number of Cypris 
was placed under identically the same conditions, except that 
the eggs were absent. Im 18 days all the Cypris in the 
first culture were dead; in the control I counted 220 living 
