300 



ROBERT A. BUDINGTON. 



one another always, for there may be no constancy in this detail 

 of relations; the laterally side-by-side position, however, would 

 seem better to permit approximation of each copulatory organ to 

 the intra-atrial opening of the uterine duct of its mate. 



G.a. 



FIG. 2. Diagram of two mating worms cut transversely at level of the genital 



atria. G.a., Genital atria. 



Impregnation in this species is thus mutual and simultaneous 

 between the members of a pair. The period of time over which 



FIG. 3. Outline drawings of two ex-copulant flatworms after fixation. The penes 



still protrude. 



they maintain this relation was not secured as it seemed desirable 

 to fix the worms while copulation was in progress. Fig. 3 shows 

 careful outlines of the two excopulants after fixation, showing 

 relative size of body to copulatory organ, etc. 



