136 DR. J. STEPHENSON ON THE MORPHOLOGY, CLASSIFICATION, 



their funnels, and the alimentary canal is excluded. The testis 

 sacs have similar relations ; and if the ovarian chamber were to 

 lose its nephridia, and to become divided into two, one for the 

 organs of each side, we should have an identical condition 

 reproduced. It is difficvilt to resist the conclusion that the testis 

 sacs owe their origin to the same process which we can see and 

 follow in the case of the ovarian segment. 



Beddard, so long ago as 1891 (6), suggested this origin for the 

 testis sacs ; he thinks they " may be all that is left of the ccelom 

 belonging to the segment which contains the testes." He adds : 

 " This is of course no more than a suggestion"; and, so far as I 

 know, the suggestion has never since been considered. But 

 I believe that the above considerations show with some degree of 

 probability that this is really the true nature of the sacs. 



(3) The Relationships of the Genera of Moniligastridce. 



In the present section I omit the consideration of the recently 

 discovered genus Syngenodr'dus, to which reference will be made 

 later, and confine myself to the previously known genera of 

 the family. 



The most primitive of the four genera is Desmogaster, in which 

 the sexual organs are arranged as shown in the accompanying 

 figure (text-fig. 11). I use letters to indicate the several segments, 

 since it is easier thus to make comparisons between this and 

 other genera. 



Text-fiffure 11. 



Spth 



t sac nif vd- o 



ovis 



Desniocj aster. Z./i., last heart : j»^.. male funnel; o., ovaiy; o^., ovarian 

 funnel; oi'is., ovisac ; spf/*., sperraatlieca; if., testis ; ^.sac, testis sac ; 

 ■v.d., vas deferens. 



There may be either one or two pairs of spermathecse ; two 

 pairs are shown in the figui^e, but if only one pair is present it 

 may be either the anterior or the posterior. 



Eupolygastei- is derived from Desmogaster by the disappearance 

 of the posterior set of male organs and the anterior sperma- 

 thecse (the anterior spermathecse are the complement of the 

 posterior male organs ; these face each other when the worms 



