BLOOD-PARASITES OF FISHES OCOljEillNGAT EOVIGNO. 1-39 



a state of teusioii, from wliicli it relaxes, in virtue of its 

 elasticity, on tlie death of the body; in so doing it auto- 

 matically unwinds the body, at the same time causing it to 

 become more or less C-like, before actual fixation occurs. 

 In this connection it should be pointed out that Danilewsky 

 (4a), who studied trypanosomes carefully in the living 

 conditiou, frequently figured them with the undulating 

 membrane spirally wound round the body, but in some cases 

 he shows it attached along one side of the body. 



Lastly, if, as we have been led to consider, the parasites on 

 wet films are generally in a spirally twisted condition, we 

 might expect to find a slight shortening in length; this, 

 together with a certain amount of contraction due to shrinkage, 

 would be sufficient to explain the difference in average length 

 between the parasites on wet films and those on dry ones. 



In many of the parasites on Giemsa-stained smears numbers 

 of small bodies occur, which appear to be prominent granules 

 (fig. 37). They are deep black at the middle focus, but are 

 bright and glistening at the upper focus. They are not com- 

 parable to ordinary chromatoid granules, which stain more or 

 less red in colour. Moreover they are most abundant in the 

 aflagellar part of the body, especially between that extremity 

 and the kinetonucleus, a region which is generally free from 

 chromatoid grains. They are also scattered throughout the 

 body, and some, which cannot be distinguished by appearance 

 from the others, lie occasionally in or on the undulating mem- 

 brane. In wet films, stained either with iron-hesmatoxylin or 

 with Twort, the same bodies, if present, are not nearly so con- 

 spicuous. In the body generally no sign of them is to be 

 seen ; but near the aflagellar end, which is often slightly 

 vacuolated in character, a certain number of granules can be 

 seen, not stained very differently from the cytoplasm (figs. 

 54-56). We are not sure, however, if these granules are the 

 same. 



Returning to the parasites on dry smears, we have recently 

 noticed the peculiar fact that, since the individual of fig. 37 

 was drawn, all the black granules have vanished, leaving only 



