274 PROCEEDINGS OF THE ACADEMY OF [JuilG, 



Judging from the stages that I have been able to find, the parasite is 

 undoubtedly a Sporozoan belonging to the order Haplosporidia. It 

 does not fit in very well with the present scheme of classification of the 

 Haplosporidia; but until its complete life history is known, I do not 

 think it advisable to create for it a new genus. I shall, therefore, 

 place it temporarily in the genus Bertramia (Caullery and Mesnil, 1897). 

 As the parasite is apparently a new species, it may be known as 

 Bertramia bufonis. 



The youngest stage of the parasite that I have been able to find is a 

 small, round or oval body with a diameter of about two microns 

 (plate XXII, fig. 1, a). The cytoplasm is uniformly granular and the 

 nucleus, which occupies the centre of the cell, is round or somewhat 

 irregular in outline. The nucleus is composed, apparently, of a dense 

 mass of chromatin, as it always appears homogeneous and stains 

 intensely black with the iron-hsematoxylin. 



After the young parasite enters one of the ova of Bidder's organ it 

 divides repeatedly, forming a number of cells similar to that shown 

 in fig. 1, a. Cell division undoubtedly takes place by means of karyo- 

 kinesis, as I have found several cases like that of fig. 1, b, in which 

 faint traces of a spindle can be seen and also irregular masses of chro- 

 matin collected at the spindle poles. After the division of the chro- 

 matin, the daughter-nuclei assume a rounded shape (fig. 1, c), and 

 subsequently division of the cjrtoplasm takes place, (fig. 1, <i). Some- 

 times, as shown in fig. 1, e and /, one or both of the cells will have begun 

 a second division before the first division is entirely completed. All 

 of the stages shown in fig. 1, a-f, may be found in a single section of one 

 of the large ova of Bidder's organ. 



The period of multiplication is followed by a growth period in which 

 each of the cells increases enormously in size and the nucleus divides 

 a number of times without any corresponding division of the cytoplasm 

 (figs. 2-5). The nuclear divisions at this stage of development are 

 evidently also mitotic (fig. 3), although on account of the small size 

 of the spindle and of the chromosomes it is quite impossible to make 

 out any details of the process. 



At a comparatively early stage in its development the trophozoite 

 becomes surrounded by a thin membrane (fig. 4), which later forms a 

 cyst wall enclosing the spores (fig. 7). The full-grown trophozoite has 

 a diameter of 9-11 microns, and contains a large number of deepl}' 

 staining nuclei which are usually irregular in outline (fig. 5). The 

 multinucleated body soon segments into a mass of spores (fig. 6), 

 which become round or oval as soon as separation is effected (fig. 7). 



