ON THE STRUCTURE OP VERMICULUS PILOSUS. 263 



terminate in flame-cells, while the canal itself is provided with 

 '^ flames " at intervals along its conrse ; it seems not impro- 

 bable that the flame-like cilia of the nephridiostome of Vermi- 

 culus represent the *' flame " of the terminal cell, and the cilia 

 of the ampullae represent the " flames '' distributed along the 

 course of the canal in the Planarian. Possibly the arrange- 

 ment found in the large nephridia of the Earthworms, described 

 by Benham (1), in which whole tracts are ciliated, is derived 

 from some such system as we find in Vermiculus and the lower 

 Oligochsetes by the extension of the cilia over a great length 

 of the canal. ^ 



The late development of the median spermiducal chamber 

 is another of those characters quite peculiar to our worm. 

 What the function of this chamber may be it is difficult to 

 conjecture ; perhaps it acts as a sucker during copulation ; the 

 disposition of the muscles would favour this supposition. How- 

 ever, it must be noticed that besides the formation of the 

 spermiducal chamber, the apertures of the genital organs them- 

 selves show a distinct tendency, as it were, to unite in the 

 middle line. This is clearly seen in the case of the male pores, 

 which come close to each other ; but more especially in the 

 case of the spermathecal pores, which become actually con- 

 fluent. As a striking contrast, we may compare such a form 

 as Heterochseta, in which, as described by Benham (2), the 

 sperm-ducts and spermathecse open above the ventral setse! 



The fact that Bothrioneuron, described by Stole (5), possesses 

 a median male pore might suggest a close relationship between 

 the two worms, but they differ in other particulars most 

 markedly from each other. The setae, nervous system, and 

 nephridia of Bothrioneuron are all very diff'erent from those 

 of Vermiculus ; it possesses commissural vessels, a prostate, a 

 complicated system of genital setse, and no spermathecse. 



On the whole, it must be concluded that Vermiculus stands 



1 Since this was written, Professor A. G. Bourne has in this Journal 

 (vol. xxxvi, 1894, "On Moniligaster grandis") described somewhat 

 similar undulating bundles of cilia, which, however, are attached at both ends, 

 not hanging freely in the canal as the cilia do in the ampullae described above. 



