76 H. ir. WOODCOCK. 



already shows the commencement (see above^ p. 5). A 

 most interesting stage in this rednction is exemplified by 

 Urospora lagidis (and also by Gonospora varia), 

 recently described by Brasil (loc. cit.). Both kiuds of 

 gamete are here of about equal size and alike in shape. 

 There is^ however, a sharp nuclear distinction apparent. The 

 nuclei of the elements proceeding from one half of the cyst 

 are smaller and chromatically denser than those belonging 

 to the gametes from the other half.^ The former are pre- 

 sumably male elements and the latter female, though this is 

 not explicitly stated by Brasil. 



The final stage is that of complete isogaray, where there is 

 no discernible evidence of sexual difi'erentiation whatever, at 

 any rate in the gametes themselves. Typical instances are 

 those of Gregarina, Lankesteria, and Diplodina, all of 

 which have been discussed above. Nevertheless one may, I 

 think, regard binary association as itself, in a measure, 

 physiological evidence of sexuality. And, indeed, in a few 

 instances (e.g. Aggregata vagans, Stenophora varians, 

 Pterocephalus, and Diplocystis clerci) there are mor- 

 phological differences between the two associates which 

 Leger (22) is inclined to consider as indications of sexual 

 differentiation. If, then, one may ascribe binary sex to the 

 parent individuals (associates), even where the gametes are 

 completely isogamous, this wonld explain why, in most cases, 

 association is binary, and why sporulation is unsuccessful in 

 the triple syzygies commented upon above. 



Unusual and specially modified forms. — While in 

 most of the ccelomic Gregarines actual copulation is evidently 

 still necessary, since the trend of development has been to 

 insure a lasting union, there are, on the other hand, one or 

 two forms known in which conjugation of the gnmetes — i. e. 

 the true sexual process — can be apparently dispensed with. 

 The starting-point of parthenogenesis in the order is pei'haps 

 seen in instances where we find both conditions, copulation 



' An almost similar stale of things is really presented also by M onocystis, 

 wliicli lias been lately re-examined by this same worker (4). 



