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Transactions. 



than that of more typically meganephric worms, but there is only one in 

 each segment, which fact is a further indication of the meganephric con- 

 dition of the worm. Unfortunately, 

 the preservation of the worm was 

 not sufficiently good to allow of the 

 study of detailed histology : what 

 could be observed of the nephro- 

 stome is given in fig. 5, taken from 

 a Series of sections cut transversely 

 and stained in borax carmine. The 

 funnel is seen to consist of a central 

 cell and marginals. It is cup- 

 ahaped, and not unlike the distal 

 portion of the funnel of Maori- 

 drilus, except that the latter is larger and its marginals are more dis- 

 tinctly Seen. There ap2)ear to be no cilia on the central cell of Perieo- 

 drilvs. The marginals are bent inwards from the back of the cup to 

 form a hood over the cavity of the frmnel — fig. 5 (&) — so that a section 

 from side to side near the back of the funnel does not show an opening 

 to the coelom. 



There is no doubt as to the presence of a central cell, the nucleus of 

 which may be distinctly seen {n.c.) in fig. 5 {a). 



Fig. 5. — Perieodrilus ricardi. Three con- 

 secutive sections — (a), (6), (c) — through 

 the funnel. 



Perieodrilus montanus. 



The nephridium of this species is similar to that of P. ricardi. It has 

 the same diffuse form, on account of which the worm was originally con- 

 sidered to be micron ephric (see figs. 6, 7). P. montanus is smaller than 

 P. ricardi, and the size of the nephridial tube corresponds with the smaller 



Fig. 6. — Perieodrilus montanus. Three segments, not consecutive, from the mid- 

 body, showing the variation in the looping of the nephridia. 



size of the worm, the tubules being much finer and more delicate in the 

 former species. A worm 12 mm. in diameter, the body-wall when laid 

 open and flattened out measures 30 mm. across, the nephridial coil is 5 mm. 

 in length and commences 2 mm. from the nerve-cord. 



