1908.] BLOOD-PARASITE OF WHITE MICE. 711 



The nuclear membrane is definite. It has a somewhat beaded 

 appearance in some stained preparations and that can also be seen 

 in living material (PI. XXXIX. figs. 2, 4, 6, 16). Extra-nuclear 

 chromatin also occurs, for in favourably stained specimens, a 

 chromatic cap can be distinguished at either end (PI. XXXIX. 

 fig. 15), and isolated granules also occur (PI. XXXIX. fig. 8). 



(b) The vermicides o/ Haematopinus spinulosus. 



The vermicules of the lice present the following appearance : — • 



Their ectoplasm is not well differentiated from the endoplasm, 

 but indications of myonemes are present and are best seen at the 

 ends of the organism. 



The endoplasm is granular and much as in the trophozoites, but 

 marked concentrations of granules do not occur. 



The nucleus in some appeai^s to lie in a vacuole, and in most 

 specimens there is a clearer portion in the neighbourhood of 

 the nucleus. Its chromatin is more abundant than in the blood- 

 inhabiting forms, and the nuclear membrane is fairly distinct 

 <P1. XXXIX. figs. 23, 241. 



These vermicules were about 8'8^ long and l-4ju broad. 



YIII. Multiplication, 



(a) Schizogony. 



Examination of bone-marrow showed the presence of small, 

 oval cysts (cytocysts) about 13"l/i long by 8*9^ broad (PL XXXIX. 

 fig. 20). These contained relatively few (about 12) but distinct, 

 small forms with a definite vermicular or reniform contour. 

 Each of these small vermicules was about 4*4 long by "8^ broad 

 (PI. XXXIX. fig. 20). They are the merozoites, produced by 

 the multiple or asexual fission of a schizont inside the cytocyst. 

 The general protoplasm was granular. Remains of the nucleus 

 of the leucocyte host were seen on the side of the cyst. Inside 

 the cyst were also some remains of the residual protoplasm of the 

 schizont. By the dehiscence of the cyst these merozoites are set 

 free in the blood-plasma, where they become vermicules or young 

 trophozoites. 



(b) Possible Association of Trophozoites. 



Two parasites lying in one corpuscle were observed (PI. XXXIX. 

 fig. 21), or two which had just left the corpuscles (PL XXXIX. 

 fig. 22). One such case, of two parasites lying in the remains of 

 a leucocyte, suggested possible association (PL XXXIX. tig. 21). 

 Here the two forms, partially free from the host-cell or leucocyte, 

 came in contact with one another and became enveloped in a 

 common cytocyst. The nucleus of one appeared to come nearer the 

 area common to the two than the other, and a chromatin mass 

 was seen in the common area of the couple. This suggested that 

 transference of chromatin takes place from one parasite to the 



