S. R. Christophers 
41 
pouches of the diverticulum wall. In this latter case the sporocysts 
would easily pass through the neck of the pouch into the lumen of the 
diverticulum. If sporozoites, the result of a previous nymphal infection, 
occur free in the gut of the adult tick during the act of engorgement, 
it would not be very difficult for them to pass at this time into the body 
of the second host. 
Development of other mammalian haemogregarines in 
arthropod hosts. 
In my description of H. gerhilli, a haemogregarine found in the red 
blood corpuscles of the common Indian Jerboa Rat {Gerhillus indicus), 
I described what I took to be developmental stages of this parasite in 
the louse (Haematopinus stephensi) commonly found infesting these 
animals, i.e. free vermicides in the gut and large cysts containing 
numerous sporocysts in the body cavity. For several reasons, notably 
Patton’s failure to find similar cysts in lice fed on squirrels infected with 
L. funambuli, I thought later that I might have fallen into one of the 
frequent errors connected with the tracing of the cycles of development 
in supposed or known carriers. But the large cysts in this case are 
indistinguishable from those associated with the development of L. canis 
in the tick, and with those described by Miller in that of H, perniciosum 
in the mite. This fact, taken in conjunction with the results of 
dissections of lice from infected and uninfected gerbilli given in my 
paper, makes it more than probable that I had correctly described these 
cysts as a portion of the extra-corporeal cycle of the haemogregarine in 
question. 
Following my description of the cysts in Haematopinus, Balfour (s) 
noted similar large cysts in the case of a flea (P. cleopatrae), caught 
on jerboas infected with H. jacidi, also a haemogregarine attacking 
the red corpuscles of the host. Under the impression that the cysts 
described by me were not a stage in the development of H. gerhilli, as 
first described, he failed, except at first, to attach much importance to 
the occurrence of the cysts in the flea. But again there is the possibility 
that he was correct in his first assumption that the cysts in the flea 
were a stage in the extra-corporeal cycle of H. jaculi. 
Miller (4) in the case of H. perniciosum, a haemogregarine attacking 
the leucocytes of the white rat, has described in the body of the mite 
Lelaps echidninus, a cycle of development exactly parallel in its main 
features to that outlined for L. canis. 
