1907.] A NEW H^MOGREGARIXE. 1099' 



The intra-corpuscular forms, in their youngest stages, are placed 

 at the side of the nucleus of the blood-corpuscle, which is then 

 normal in appearance, with the nucleus occupying its proper central 

 position. When the parasite is full-grown, however, the nucleus 

 of the corpuscle is more or less pushed to one side, and may become 

 somewhat irregular in outline ; but in no case have I seen the 

 corpuscular nucleus at all broken up, as is known to occur in many 

 cases of reptilian htemogregarines, hence classed by some authors 

 as a distinct genus Karyolysii,s. I have observed, however, a 

 peculiar relation between the shape of the parasite and the 

 displacement of the corpuscular nucleus. The intra-corpuscular 

 parasite is always distinctly sausage- shaped, and slightly bowed 

 in the plane of the corpuscle. It is reasonable to attribute this 

 curvature to the fact that the parasite, being situated to the side 

 of the corpuscular nucleus, accommodates itself to the space in 

 which it lies (compare figs. 5 & 6, PI. LY.). We may sjoeak of this 

 as the normal curve of the parasite. But in a few cases we find 

 the curve of the parasite entirely reversed, and its convexity 

 turned towards the nucleus of the corpuscle (PI. LY. fig. 8, PI. LYI. 

 figs. 20, 21). In such cases two points are noticeable : first, that 

 the parasites resemble the free forms very closely ; secondly, 

 that the corpuscular nucleus is much more displaced than usual, 

 being sometimes pressed quite against the side of the corpuscle 

 (figs. 8 & 20). This point has also been noticed by Lt.-Col. 

 Wyville- Thomson, who has sent me four sketches of the parasite, 

 representing one free and three intra-corj)uscular forms : two of 

 the latter show the normal curvature of the parasite, like my 

 fig. 19 on PI. LYI.; the third, however, shows a reversed curve, 

 with the nucleus of the corpuscle pushed far to the side, as in my 

 fig. 20. I think we shall not be far wrong in attributing these 

 cases of reversed curvature to the commencing activity of a 

 parasite about to become free from the corpuscle, in which the 

 movements of the contractile body not only alter its curvature, 

 but also may have the effect of forcing the nucleus of the corpuscle 

 away to one side. 



I will now proceed to describe the structure of the parasite in 

 more detail. Beginning with slides A and B, we find forms of 

 the parasite which may be classified as young intra-corpuscular 

 forms, full-grown inti^a-corpuscular forms, and free forms or 

 vermicules. 



The young intra-corpuscular forms (PL LY. figs. 1-5) vary in 

 length from about |-| of the blood-corpuscle ; i. e., from about 

 9-11 yu in length*. They were remarkable in two points: first, 

 their very clear cytoplasm, hyaline and free from granulations, 

 so that they often have the appearance of a space in the blood- 

 corpuscle ; and, secondly, their delicate nucleus, which appears to 

 consist of faintly-staining granules and strands of chromatin, 



* Since all the figures which accompany this memoir are drawn to a magnification 

 of 2000 linear, it follows that a length of 2 mm. in the drawings corresponds to an 

 actual length of 1 ju in the objects. » 



Pkoc. Zool. See— 1907, No. LXXIII. 73 



