70 IT. M. WOODCOCK. 



wall is formed, and the animals soon die off. Siedlecki 

 (loc. cit.), Leger [19] and Brasil [3] give examples wliere 

 one memljer of a couple has produced primary sporoblasts in 

 a normal manner, while the other, most likely because the 

 above condition was not fulfilled, has remained stationary 

 and, indeed, succumbed. One C4regarine of a couple can in 

 certain cases, apparently, exert sufficient influence upon its 

 associate to induce it to commence sporulation, although it 

 itself may not be ripe enough to do so, and as a result not 

 only does it not benefit by the stimulus or " Reiz " of the 

 other, but this, on the contrary, appears to harm it and it 

 succumbs instead. 



(11) General Significance op Association. 



Descent of the Telosporidia. — We are thus led to a 

 consideration of the origin and significance of association in 

 general. We may commence by endeavouring to trace the 

 descent of the Telosporidia — that sub-class of the Sporozoa 

 which includes the Gregarines — from a Flagellate stock. 

 For Schaudiun (33) has recently demonstrated that a certain 

 malarial parasite of birds, namely Halteridium nocture, is, 

 in reality, only a phase in the life-cycle of a Trypanosome, and 

 it is becoming increasingly probable that the Hfemosporidia 

 as a whole are derivable from, and in many cases still 

 closely connected with, Hfemoflagellates. There can be 

 little doubt that the Coccidia and Gregarines have an 

 origin similar to that of the Haemosporidia, for the first- 

 named are closely allied to this order, and the differences 

 exhibited by the Gregai-ines are easily understood when their 

 somewhat different relation to the host is borne in mind. 

 Hence it appears most likely that the whole of the Telo- 

 sporidia have originated from a Flagellate ancestor.^ 



In the case of the Haemosporidia the original parasitic 



' This ancestor may be assumed to liave been of a fairly generalised type, 

 such, for instance, as tliat whose life-history is outlined by Dofluin (11), 

 p. 53. 



