27] PROTEOCEPHALIDAE — LA RUE 27 



retraction. In many species the muscle fibers connecting the cirrus with 

 the walls of the cirrus-pouch seem entirely too weak to assist much in 

 this process. Since the inner end of the cirrus-pouch is attached to the 

 body wall by strong muscles their contraction would lengthen the cirrus- 

 pouch and this would exert a direct traction upon the ductus ejaculato- 

 rius. Such a lengthening of the pouch would tend toward the produc- 

 tion of a negative pressure which might draw the cirrus back into the 

 pouch. In some species large numbers of cirri have been seen protruded, 

 in others none or almost none. Protruded and unprotruded cirri have 

 been noted among both mature and ripe proglottids. These facts stimu- 

 late one to inquire whether the cirri are normally retracted after pro- 

 trusion? Is protrusion of the cirrus a common occurrence in the act of 

 copulation or is it an accident? Had those unprotruded cirri in the 

 ripe proglottids ever been protruded? These are questions that cannot 

 be answered from the available data nor has the author seen anything 

 in the literature on these points. An opportunity is suggested here for 

 experimental work. 



/^iggenbach (1896) considered that the broad cavity of the cirrus 

 might be called a vesicula seminalis and that this cavity functioned as 

 such an organ. While it is true that the cavity of the cirrus and ductus 

 ejaculatorius might function as a vesicula, they are not structurally a 

 vesicula. When the sexual organs become fully mature the semen is 

 stored until ejaculated in the coils of the vas deferens which become 

 greatly swollen. Thus the coils of vas deferens function as a vesicula 

 seminalis altho they are not. differentiated into such an organ. JProperly 

 speaking there is no vesicula seminalis in the Proteocephalidae. The 

 vasa efferentia and vas deferens have been carefully described by Rig- 

 genbach (1896) and La Rue (1909). Altho they have been observed in 

 a number of species of the family they have not been especially re- 

 described in the descriptions of the species because they are essentially 

 the same in all species of the group. Their general relations may be seen 

 in figures 90 and 180. The vasa efferentia are thin walled small tubes 

 leading out from the covering of the testes. These tubules anastomose 

 with some of their neighbors and finally the larger vessels unite with the 

 inner end of the vas deferens. The vasa efferentia can sometimes be 

 studied from toto preparations of proglottids if the testes were discharg- 

 ing semen at the time of killing the cestode. Carefully made frontal 

 sections stained with haematoxylin sometimes show them very well. The 

 vas deferens is a thin walled tube of larger diameter than the vasa effer- 

 entia. It begins near the middle of the proglottid on the inner dorsal 

 surface of the muscle sheath. Then it makes a few or numerous coils 

 which extend to the inner end of the cirrus-pouch which it enters. From 



