88 n. M. WOODCOCK. 



morpliological separatencss and individuality excepting in the 

 plane of union, although, from the nature of the case, this is 

 not apparent. 



(11) Seeing the efforts made by these non-motile ccelomic 

 parasites to insure association, we are naturally led to try and 

 account for its obvious importance. 



The resnlt of recent research points strongly to the con- 

 clusion that the Telosporidia, as a whole, are descended from 

 a Flagellate ancestor. This ancestral Flagellate would possess 

 motile gametes, which were, probably, more or less aniso- 

 ganious. Such an ancestor we may regard as being common 

 to the three Telosporidian orders, namely the Gregarines, the 

 Coccidia, and the Haemosporidia, the differences exhibited by 

 them being easily understood when their different habitat and 

 degree of parasitism are borne in mind. 



Of these orders the Gregarines are by far the most success- 

 ful, this being undoubtedly due to their possession of the power 

 of association. Hence, if this were a primitive condition, it 

 would almost certainly be apparent (as such) in the Coccidia, 

 since by it sexual conjugation is rendered piactically certain. 

 The state of affairs in that order seems to show conclusively 

 that association is not a primitive, but rather an acquired, con- 

 dition, one which has been acquired to any extent only by the 

 Gregarines. 



I regard the power of cytotactic attraction as having 

 become so developed and specialised in this order that the 

 formation of gametes is now entirely regulated by and de- 

 pendent on such cytotactic influence; in other words, asso- 

 ciation is most probably necessary for sporulation to take 

 place. There is abundant evidence to show that, in most 

 forms at any rate, this is undoubtedly the case. Correlated 

 with this, differentiation of the gametes is no longer necessary, 

 and a beautiful series of stages exemplifying the gradual tran- 

 sition or reduction from anisogamy to isogamy is now known. 



The above view seems to me much more probable than the 

 opposite one, namely that association is a primitive condition 

 tending to become less important with increasing anisogamy. 



