BLOOD-PARASITES OF FISHES OCCUERING AT ROVIGNO. 141 



smaller than the full-sized ones ; and many of Neumann's 

 figures of T. variabile I'esemble strongly these smaller 

 forms. In fact, neither from Neumann's description nor from 

 his figures is there any reason to suppose that T. variabile 

 is not a synonym of T. raia3. 



Comparison of the Nuclear Structure of a Hjiimogregarine 



WITH THAT OP A TrYPANOSOME. 



A most interesting and important result of our study on 

 the above-mentioned blood-parasites of fishes is afforded by 

 the evidence it has given us of the essential difference between 

 the nucleus of a h^emogregarine and the trophonucleus of a 

 trypanosome. This difference is brought out forcibly by all 

 the three methods of technique employed, though, of course, 

 one method may show a certain feature or detail better than 

 another. 



Considering first the case of Hsemogregarina rovig- 

 nensis in Trigla sp., the conclusion arrived at by comparing 

 and combining the impressions given by different stains is 

 that the nucleus in this parasite consists of a regular or 

 irregular meshwork or reticulum, itself chromatic or impreg- 

 nated with chi'oinatin, on which are suspended chromatin 

 grains and masses of varying size and form. The reticular 

 ground-work is best seen in iron-h^ematoxylin or Twort pre- 

 parations (figs. 39-50, 59-64) ; in the latter it is always 

 distinctly red (chromatic) in colour. The limit or border of 

 the nucleus appears to be itself part and parcel of the 

 reticulum, the peripheral segments of the latter being usually 

 arranged so as to give a fairly regular oval contour or 

 "membrane." This structure is well shown in figs. 48 and 

 49 of large forms. Hence one cannot speak here of a true 

 nuclear membrane as something distinct and sepai"ate from 

 the general nuclear substance. This "membrane" also has 

 numerous chromatic granules strung upon it; these are 

 generally smaller than those occurring in the more central 

 parts of the reticulum. The chief chromatic aggregations 



