BY E. J. GODDARD. 791 



the latter species; and the spermathecal duct in this region is 

 much more strongly developed, as regards size and musculature, 

 than the portion continued forwards from this region to reach 

 the ovisac-structure. From this it seems certain that Astacopsi- 

 drilus has been derived from a Phreodrilan stock; and that, 

 judging from the fact that A. notabilis shows, in the case of its 

 spermathecse, a tendency towards fusion, and that this fusion is 

 complete, and no traces of any spermathecal pore can be seen in 

 A. fusiformis, the former is the older species. 



It is noteworthy that in the two Australian genera of the 

 family, Phreodriloides Benham, and Astacopsidrilus gen. nov., the 

 variation of most significance with regard to Phreodrilus Bed- 

 dard, is in connection with the spermathecse — structures which 

 are of the greatest importance in connection with the family 

 from the point of view of classification and also phylogeny. It 

 would really seem that these structures have already disappeared 

 in Phreodriloides, and that the muscular sac is not the represen- 

 tative of a spermatheca which has moved forwards, but has been 

 evolved independently; further, that the posteriorly situated 

 spermathecse in Astacopsidrilus are very unstable. 



The Phreodrilidce, occupying the position usually assigned to 

 them in the plrylogenetic table, namely, as intermediate between 

 the Lumbriculidce and Tubificidce, had possibly been derived from 

 the Lumbriculid stem (or from the Tubificid stem) after the evolu- 

 tion of posteriorly situated spermathecse in that group; and one 

 of the lines of variation along the Tubificid stem may have 

 already been opened up before the Phreodrilidce left that stem, 

 in the way indicated by the disappearance of these posteriorly 

 situated spermathecse, as foreshadowed in Astacopsidrilus, and the 

 evolution of new spermathecse after the fashion of that in 

 Phreodriloides. 



In conclusion, I may mention that I had the privilege of 

 examining some specimens of Astacojjsis bicarinatus sent from 

 Victoria by Professor Baldwin Spencer, but was unable to detect 

 any trace of Oligochseta in association with them. 



