38b Mr. T. Bentham on some 



its larger stages lying alongside the nucleus of the host-cell. 

 The smaller forms were always definitely rounded in shape, 

 resembled Plasmodia, and never more than two were to be 

 seen in a single erythrocyte (see PI. XVII. tig. 1,5 & 6). The 

 largest were never more than 8 /a in length by about 5 fx in 

 breadth at the widest part of the body. It was at first 

 thought that, owing to their pale colour, they were merely 

 capsules of some hsemogregarine that had left the host-cell ; 

 but, as no other forms were found anywhere else free in the 

 plasma, and as also the cytoplasm, even after prolonged 

 staining, was of the palest blue*, they were then taken to be 

 definite parasites. Moreover, a small nucleus of the diffuse 

 type could with difficulty be made out. This was very small, 

 and not, as a rule, centrally placed, but occupied a place in 

 the cytoplasm at one end of the cell-body. Sometimes, as in 

 the other parasites, two forms were found in a single host- 

 cell. These either lay side by side or overlapped one 

 another when on one side of the nucleus; but they often 

 occurred away from one another and on opposite sides of the 

 nucleus. No metachromatinic granules were present in this 

 organism. From the paleness of the coloration of these 

 parasites and from their badly staining diffuse nucleus, it 

 was at first thought that they were the microgametocytes of 

 the forms found in the lymphocytes; but this seemed hardly 

 likely, since they were found by themselves in one fish. 

 Besides this, these forms were smaller and differed markedly 

 from the others in shape and in their disposition towards the 

 host-cell nucleus. It also seems inconceivable that two types 

 of the same parasite should choose different host-cells. 



It is a difficult matter to determine the true character of 

 these parasites, but it seems that the organisms in the erythro-* 

 cytes are, at any rate, Hsemogregarines, the character of the 

 other specimens being decidedly uncertain. 



Parasites of Raia batis {the Common Skate). 



In the single fish examined a large number of small 

 Haniogiegarines were found. They were so numerous in 

 the blood that at least 10 % of the erythrocytes were found 

 to be infected, and occasion idly a few parasites were found 

 free in the plasma, They were all small vermicular forms, 

 measuring about 7 /a in length by about 2 /a in breadth. In 

 some cases the parasites were pointed at both ends (see 

 PI. XVII, fig. 2, 1 & 2), but more usually one end was 



* The paleness of the cytoplasm was reminiscent of that exhibited by 

 certain Piroplasmata, but the nucleus was not nearly so prominent. 



