ANATOMY AND CLASSIFICATION OF THE ARENICOLID.?]. 525 



vitelline membrane. Young ova are found along tlie axis of 

 each process in close association with the vessels which 

 traverse the process. They are, in fact, formed from the cells 

 covering the vessel, just as are the gonads of other species 

 (PI. 26, fig. 51). 



The vessels passing into the processes are at first blind 

 outgrowths of the gonidial vessel (as recorded by Fauvel, 

 1899, p. 27) ; but later, when two or more vessels are present 

 in one process, there are transverse connections which place 

 the vessels of the process in intimate communication with 

 each other (fig. 52). These vessels are probably homologous 

 with the tuft of blind vessels given off from the gonidial 

 vessel of A. Claparedii (PI. 24, fig. 26), but in the latter 

 species they are not associated with the gonad, their cellular 

 covering being chlorogogenous. 



The genital strand of the female A. ecaudata, which is of 

 considerable thickness, is covered by a layer of unaltered 

 epithelium, which also covers each process, and which is 

 ruptured when the ova are shed into the coelom (fig. 51). 

 The genital strand and the processes arising from it, may be 

 regarded as the ovary of this species, which thus reaches a 

 greater size and complication than that of any other species 

 of Arenicola. 



In males there are also two strands commencing on each 

 nephrostome and running backwards, the one only a short 

 distance, but the other closely applied to and along nearly 

 the whole length of, the secreting portion of the nephridium. 

 Only the latter, which is on the inner side of the nephridium, 

 gives rise to gonads. From this strand there is produced on 

 the inner side towards the middle line, one (or in some cases 

 two or three or even four) pinkish, greyish, or milk-white, 

 thin reniform outgrowths, which may attain a length of 

 5 mm. to 7 mm., and a breadth of 3 mm. to 5 mm. (fig. 48). 

 The thickness of these reniform sacs is only about a milli- 

 metre. Each contains spermatozoa in all stages of develop- 

 ment. The gonidial vessel which runs through the genital 

 strand gives off several branches into the reniform lobe. 



