THE CHROMATIN MASSES OF PIROPLASMA BIGEMINUM. 321 



chromatin mass or masses. Usually there was more than oue 

 chromatin mass in each parasite (see pi. 18, figs. 1 to 7). 



(2) In the pyriform and ovoid parasites there are usually 

 present (a) a rather large and dense chromatin mass — the 

 nucleus ; (|3) a second, somewhat smaller, usually denser 

 mass of chromatin — the blepharoplast, which is sometimes 

 only punctif orm ; and many parasites possess in addition (7) a 

 rather looser mass of chromatin, of a woolly or mesh-like 

 structure (chromidial reticulum). 



(3) Variations occur in the relative positions of these 

 chi'omatin masses, and less frequently in their relative sizes. 

 These variations may be due in part to the parasite being 

 viewed from different aspects. 



(4) The loose chromatin mass is often relatively well- 

 marked in P. bigemiuum. 



(5) Free parasites were sometimes seen in which the 

 pyriform contour was slightly modified, and the apical end 

 prolonged into a short cytoplasmic process. Such forms 

 possessed a nucleus and blepharoplast, and somewhat re- 

 sembled Hsemoflagellates (text-figs. 40 to 42). 



(6) In round forms nuclear dimorphism also probably 

 occurs, for there is usually more than one chromatin mass 

 present (text-figs. 27, 28, 43, and 44). Amoeboid forms were 

 not available for examination. 



(7) The cytoplasm of P. bigeminum appears to be 

 vacuolated in character. Unfortunately, the observations 

 were, of necessity, confined to stained preparations. 



(8) The possible significance of these results is briefly 

 discussed in the preceding section. More definite pronounce- 

 ments are premature, pending further knowledge of the 

 developmental stages of Piroplasma in the tick. 



December 31st, 1906. 



Addendum. 



Since writing the foregoing, two papers have appeared 

 relating to Piroplasma (Babesia) canis, one by Chris- 



