520 JOSEPH STAFFORD, 



organization of tliis is the most difficult task we meet in the study 

 of the sexual system. I shall therefore present a simplified scheme 

 which will not only exemplify the essential structure of this organ 

 but also the manner of arriving at that structure in the ontological 

 development of the animal. 



Let us suppose that the vesicula seminalis originally continued as 

 a narrow, straight tube — the ductus ejaculatorius — through the 

 centre of the penis sack. And then by a course of uniform, rapid 

 growth in the walls of the ductus from the point where it passes 

 through the posterior end of the penis sack it becomes both wider 

 and longer. The increase in length in such cases of growth generally 

 occasions the bending of the part upon itself but here, as the growth 

 produces a widening as well as a lengthening, the bending or crumpling 

 is directed inwards into the ductus itself. In this way is produced 

 a papillär like forward growth (Fig. 16, 9 PP) from the distal end 

 of the cirrus sack into the greatly widened ductus ejaculatorius. 

 Consider now, further, that the expansion of the widened portion is 

 hampered by the stout penis sack surrounding it but that the growth 

 in width continues and we will have the necessary conditions for a 

 series of longitudinal foldings (Fig. 16') extending from the posterior 

 end, where the widened ductus is reflected over the papilla, forwards 

 along the sides of the expansion. That this was the order of develop- 

 ment I was convinced from a careful study of the anatomical structure 

 but I was delighted to find that sections of young animals confirmed 

 my belief. This is not all. Between ductus ejaculatorius and cirrus 

 sack is a fine meshed parenchyma and this follows in its growth the 

 development of the more rigid ductus, filling in the long furrows and 

 penetrating from the posterior between the outer wall of the papilla 

 and its central canal (inner ductus). In the adult animal the posterior 

 part of the expansion of the ductus (outer ductus) has coalesced with 

 the penis sack, the longitudinal furrows have deepened till their inner 

 folds touched and united with the outer walls of the papilla, and the 

 parenchyma of the papilla — the intervening combined walls where 

 papilla and folds meet having thinned out and become broken through 

 (resorbed). These connecting plates between inner, papillär, and outer, 

 penis-sack parenchyma are the septa described by Voeltzkow. They 

 include between them a series of forwardly extending canals which 

 open anteriorly into the simple, unmodified ductus. At its broadest 

 part the bulbus has about a dozen radiating septa but both forwards 

 and backwards from this they are fewer so that sections in these 



