The family Koellikeriadae. 143 



Wedlia bipartita Cobb. 



Wedlia faba Cobb. = Monost. faba Bremsek. 



Probably none of these descriptions is absolutely exact since, 

 as \ve shall see, the presence or absence of suckers seems to be a 

 variable feature in these forms and rudiraentary suckers or fading 

 remnants of an atrophying- and disappearin^ sucker make it difficult 

 to decide whether tliere are two, or only one, or none. Tliis appears 

 to be the result of their perfectly inactive life in a cyst and although 

 it is probable that they all originally had two suckers, these organs 

 are now found in various stages of retrogression and their number 

 can scarcely be used as the basis for separating genera. 



With regard to the genital apparatus, close examination shows 

 that while in one of the pair the female organs are highly developed 

 and the male obsolescent, in the other the reverse is the case 

 although in both there is a fading hermaphroditism. The outer 

 form of the bodies corresponds with the predominance of the 

 respective sex development. 



Therefore specifications as to these points in the description of 

 the genus have not the same decisive importance that they have in 

 other genera and it seems on that basis that Cobbold's description 

 of Koellüeria is about as accurate as the later ones and therefore 

 by the rules of nomenclature since it is the first generic name which 

 distinguishes these peculiar forms it should be accepted. There is 

 nothing in the description given by Taschenberg for the genus 

 Bidijmosoon which would justify the abandonment of the earlier 

 genus, and his Statement that there are no suckers is even less 

 accurate than Cobbold's division of the group into Koellikeria with 

 two suckers and Wedlia with one. 



There is no good reason wliy Wedlia should not be used as 

 the generic name except perhaps that KoelliJceria appears lirst in 

 the same paper. 



It is therefore proposed to Substitute the name KoelliJceria for 

 Didymozoon throughout and the genus may be briefly redescribed 

 as foUows: 



Koellikeria (Cobbold, 1860). 



Digenetic trematodes living in pairs in cysts. Hermaphrodite 

 but sexually distinguishable by the outer form and by the predo- 

 minance in each of the genital organs of one sex with obsolescence 



10* 



