W. S. Patton 
147 
Sambon does not give us at least some hints as to how he has been so 
fortunate in finding them, especially those of L. minima, even though he 
appears not to have studied this parasite. 
When discussing the life history of the haemogregarines Dr Sambon 
begins by saying that, “ like that of other haemoprotozoa, (it) is divided 
into two cycles; a schizogonic or ‘ vegetative ’ cycle spent in the blood 
of vertebrates and characterised by asexual multiplication, and a sporo- 
gonic or sexual cycle spent in the digestive organs of blood-sucking 
invertebrates and characterised by asexual reproduction.” When 1 first 
read this statement I thought that Dr Sambon had been more fortunate 
than I have been, but as I read his papers further I discovered that he 
had not found anything whatever to show that the life history of a 
haemogregarine like that of other haemoprotozoa is divided into two 
cycles. As I have so far looked in vain for the sexual cycle of a haemo¬ 
gregarine thinking it would be something like that of the Coccidia, I 
was disappointed to find that after all Dr Sambon had discovered it was 
like that of other haemoprotozoa. Exactly what haemoprotozoa he refers 
to I am not sure of; as far as I am aware the malarial parasite is the 
only one whose life cycle we know with any certainty. Dr Sambon is 
evidently sure of the life cycles of some other haemoprotozoa, possibly 
he refers to the trypanosomes. I need hardly remind him that as far as 
we know at present these parasites do not pass through the two cycles 
referred to above. 
Under the heading “schizogonic cycle,” Dr Sambon says that “in 
examining fresh blood (the italics are mine) from vertebrates harbouring 
haemogregarines we find these parasites usually enclosed within the 
blood-cells they select for their development,. For convenience of 
description we may distinguish three principal forms: Young forms, oval, 
fusiform, or club-shaped, with nucleus median, large, round or oval, 
homogeneous. At first they are free within the stroma of their host-cell; 
later encapsuled. Adult sporonts, club-shaped, more or less bulky, 
usually doubled up, always encapsuled, nucleus median, with chromatin 
filament forming a more or less open skein, or broken up into rods. 
Host’s cells as a rule unaltered.” Here we have a statement that 
certain of these parasites when seen in the fresh blood with 
appearances described above are young forms, but how does Dr 
Sambon know they are young forms ? He gives no figures showing 
that the young merozoits just liberated, say, from a cyst in the lung of 
a snake, are exactly similar to the parasites he describes as young forms. 
Yet this description is apparently meant to hold good for all haemogre- 
10—2 
