52 H. M. WOODCOCK. 



the apparent equality between the gametes, I regard this and 

 other cases of complete isogamy iu Gregarines as constituting, 

 really, instances of binary sexuality, and not merely of exo- 

 gamy (using this term iu the sense of Hartog [12]) ; that is 

 to say, the condition we find here is deriv^ed, in all proba- 

 bility, from a typical bisexual condition, although the binary 

 sex is, in these cases, rather implied — or, more correctly, 

 potential — than actually manifest (see also below, p. 76). 

 It is almost certain that each gamete copulates with one 

 developed from the other member of the couple — probably 

 that nearest available. Although I have been unable to 

 demonstrate this point in Cystobia, for reasons which are 

 apparent from the context, there cannot be the least doubt 

 that the statement is justified Avhen the formation and consti- 

 tution of the zygote in cases of anisogamous conjugation is 

 borne in mind. The origin of the two conjugates from 

 separate associates (parent-individuals) appears to be uni- 

 versal, whether the anisogamy be strongly marked (Ptero- 

 cephalus) or only slight (Urospora). 



Absence of any movement. — With regard to the 

 mechanism of the process, I feel confident that in this case 

 there is no bustle, no tumultuous "danse des sporoblasts" to 

 be rushed through ; thanks to the remarkable extent to which 

 the intertwining is carried all is done easily and quietly. I 

 have carefully watched live cysts for long periods, both by 

 day and by night, but I have never seen the slightest move- 

 ment taking place. Now, if there had been any animated 

 movement I should certainly have observed it, at any rate at 

 the periphery ; and, moreover, in my sections through cysts 

 of this period all stages iu conjugation are to be met with, so 

 that this was evidently the right time to look for the "dance." 

 Hence I feel assured that if, at the moment of separation, 

 each gamete is not actually contiguous to a suitable fellow- 



liowever, any appreciable difference between eit.lier the two associates or the 

 gametes to which they gave rise ; nor does he state whether he observed this 

 nuclear pvu-iQcation iu elements formed from both halves of the cyst, or only 

 in those from one, which would iiavc helped to decide tlie question. 



