130 ]<;. A. MINGIIIN AND Jf. M. WOODCOCK. 



all, for the particular stimulus wliich effects the liberation of 

 these elements in the above cases is hei-e lacking, namely, the 

 fall in temperature. Lastly, it is not out of place, perhaps, 

 to refer in this connection to Miller's account of " Hepato- 

 zoon " in rats (10). In this case the sexual forms (which 

 apparently show little or no differentiation) are encysted in 

 lymphocytes. Miller found that when blood containing the 

 parasites was mixed with the expressed juices of the mite 

 (Lelaps), it was ten to thirty minutes before the host-cells 

 wei'e dissolved and thirty minutes or more in addition before 

 the gametocytes were liberated from their capsules and 

 became motile verniicules. 



From all these facts we conclude that where large free 

 verniicules of a hfemogregarine are found in the circulating 

 blood, at least in fishes, they are schizokinetes, which 

 have yet to give rise to the true sexual forms, and not them- 

 selves the gametocytes ("gametes" according to Neumann). 

 It is very doubtful whether the full-grown gametocytes of 

 haemogregarines ever become free until the blood is drawn 

 from the body.^ 



Characteristics of H. rovignensis nobis. — The prin- 

 cipal characters of this species from Trigla lineata, so far 

 as we have been able to ascertain them, are as follows : A very 

 small parasite, one of the smallest piscine hgemogregarines yet 

 described. Schizonts usually oval in form. Average size 

 (full grown?), before fission has commenced, 4*8 /ti by 2*5 yu. 

 Gametocytes large and well differentiated. Female forms 

 wide, ovoid or bean-shaped; average size 10'6 /(t by S'4/i. 

 They possess a large nucleus. Male forms fairly slender, with 

 one end somewhat club-shaped, the other end usually slightly 

 recui'ved ; average size 12 /li by 2"1 fx. These possess a small 

 nucleus. Individuals of all types may show one or two 

 characteristic granules, extra-nuclear in position, and most 

 probably achromatic in nature; they are particularly promi- 



^ From the publisliecT descriptions and figi;i-es of reptilian hfenio- 

 gregarines which we have seen we consider it most probable that a 

 similar state of affairs obtains in their case also. 



