1907.] A NEW H.EMOGREGARINE. 1103 



These figures, to which must be added the doubly-infected 

 corpuscle shown in fig. 16 from slide C, show that by far the 

 greater propoi'tion of the parasites on these slides are full-grown 

 intra-corpuscular forms. 



Comparing the results obtained from all the four slides which 

 I have been able to study, I am inclined to explain the differences 

 between them in the following way : — the parasites on slides 

 and D (PI. LYI.) are probably all of the same age, and represent 

 one generation of the parasite, possibly one infection of the host ; 

 on the other hand, in slides A and B (PL LV.) there are probably 

 two generations of the parasite, resulting, it may be, from two 

 distinct infections of the host, represented respectively by the 

 young forms (figs. 1-5) and the older, free or intra-corpuscular, 

 forms (figs. 6-15). This explanation does not, however, account 

 for the very curious differences between the nuclei seen in the 

 two cases. 



jSTo forms of multiplication were seen by me nor by Lt.-Col. 

 Wyville-Thomson, who writes : — " jSTo schizonts were found in 

 either liver or spleen, nor any multiplying forms seen in the 

 blood, all appearing to be at the same stage of development." 

 (These remarks appear, from the sketches made, to apply more 

 particularly to slides C and D.) 



Position of the Parasite. — It is evident that the parasite is a 

 typical example of the genus Hcemogregarina Danilewsky, in the 

 wide sense ; its shortness, relative to the blood-corpuscle which 

 contains it, is one of the points characterising Labbe's genus 

 Karyolysus, described originally from lizards, but now known to 

 occur also in other reptiles. It is, however, also characteristic of 

 the species of Karyolysus to cause the nucleus of the blood- 

 corpuscle to break up, which this species does not do. In any 

 case the characters by which Karyolysus are defined are hardly to 

 be considered of generic value, and its species are best i^anked 

 under Hcemogregarina until more is known about them. In the 

 species under consideration, I was often struck by its resemblance 

 to the genus HaltericUum occurring in birds, especially in cases 

 where the pai-asite is pressed against the nucleus of the blood- 

 corpuscle (compare fig. 7 on PL LV.). 



Since the species does not appear to have been described before, 

 I propose for it the name Hcemogregarina tJwmsoni, in honour of 

 its discoverer, Lt.-Col. Wyville-Thomson. Should it prove, even- 

 tually, to be the case that the pai^asites on slides A and B 

 (PL LY.) are a distinct species from those on slides C and D 

 (PL LVL), I would restrict the name to the latter. 



I should like, however, to make a few remarks about the 

 naming of new species of blood -parasites. It is a common practice, 

 which I am here following, to consider a species of blood-parasite 

 as new if it is found in a host in which j)arasites of that class 

 have not been found or described previously. The assumption 

 xmderlying this procedure is that different species of animals tend 

 to have distinct species of parasites — an assumption, however, 



