174 
II. M. WOODCOCK. 
irrowtli and extension of tlie body-cytoplasm of a smaller 
individual. I have found different stages of the process 
in my preparations. The development of the U-form 
takes \place only, so far as I have observed, in those parasites 
in which the nuclear position is that of the second type 
mentioned above. It begins by the formation of a small out- 
growth at oue end of the bod}^, which is at once curved back 
aud so extends backwards close along one side of the body 
(figs. 10, 36, 40). This outgrowth may arise either at the 
nuclear end of the parasite or at the opposite one, more 
usually, I think, at the latter. As it grows this process 
gradually forms one arm of the U, and at length the two 
a.rms become more or less equal (figs. 14, 15). Ultimately the 
two arms unite and a stout bean-shaped form results. 
In nearly all of the individuals observed in ^‘wet” 
preparations, of whichever type they may be, immediately 
surrounding the body of the parasite is a distinct space, 
which in some cases is very marked (cf . figs. 20, 22, 24-40). 
This space is probably due to the greater contraction of the 
parasite, as a result of the technique, than of the cytoplasm 
of the red blood-corpuscle enclosing it, thus causing a shrink- 
age of the former nway from the latter. In ordinary “ dry ” 
smears, stained with Giemsa, this space is also often seen, 
though not so regularly as in the other preparations (cf. figs. 
5-8, 12). In the case of the smaller parasites there is 
j)robably no definite membrane or envelope bordering the 
space on its outer side, distinct, that is to say, from the inner 
margin of the cytoplasm of the corpuscle (cf. for instance 
fig. 19, where the young Haemogregarine has obvioush" just 
entered the host-cell). In the older (larger) forms, however, 
there is certainly a definite envelope present, constituting 
a delicate but firm capsule around the parasite (cf. especially 
figs. 37-40). In the case of two of the parasites figured it will 
be noticed there is no sign whatever of the cytoplasm of the 
blood-corpuscle ; the reason for this will be mentioned shortly 
(pp. 177, 179). Hence the capsule surrounding the parasiteis 
very conspicuous. In many cases where the cytoplasm of the 
