P. Manson-Bahr and N. H. Fairley 53 
The same rule that appertains to bilharzia also appears to hold good 
for the developmental stages of other trematodes. The statistics in Table V • 
show that the Bullinus harbour the greatest number of these also in the 
month of December. The increase during this month is due to the increase 
of pigmented cercariae of Gastrodiscus aegyptius which is a parasite of the 
buffalo. According to our experience, this parasite is found mostly at this 
period of the year, and not during the height of summer, see Table V. 
Table V. 
Dissections of Bullinus contortus and Bullinus dybowski for presence of other 
cercariae (Cercariae of Gastrodiscus aegvptius, and those figured in Plate 
III, figs. 5, 6 , 7). 
Month 
Number of 
Percentage infested 
snails dissected 
as above 
1917 
May 
51 
39 
June 
27 
18 
July 
140 
31 
August 
57 
29 
September 
93 
20 
October 
No record 
No record 
November 
No record 
No record 
December 
362 
75 
1918 
January 
140 
57 
February 
72 
70-8 
March 
18 
70 
Total 
960 
54 
In summarizing these results we might state: 
(1) That in contradistinction to the observations of Looss we have 
found throughout the winter months, marked growth and multiplication 
of laval trematodes— S. haematobium, S. mansoni, Gastrodiscus aegyptius, 
and others. 
(2) That while the month of maximum infectivity for both species of 
Bilharzial cercariae was December, there was definite evidence to show that 
endemically areas are potentially infective throughout the whole year. 
Description of Non-Eyed, Fork-Tailed Cercariae found 
in Fresh-Water Snails in Egypt. 
| Only two of these were found and both are obviously not connected in 
any way with disease in man; one a very small fork-tail cercaria in Planorbis 
mareoticus from the Zoological Gardens, Giza. The other was obtained in 
4 per cent, of a batch of Bullinus dybowski in the sweet-water canal by the 
Little Bitter Lake. We have also been able to examine the cercaria of 
S. spindale from India, kindly sent bv Lt-Col. Glen Liston, I.M.S. 
