MARINE BIOLOGICAL STATION AT PORT ERIN. 185 



anatomical peculiarities, which have hitherto escaped 

 notice, with the result that no record of A. ecaudata, 

 on British shores, excepting only that made by Dr. G. 

 Johnson, can be accepted as trustworthy. Even the 

 record in the Tenth Annual Report of the L.M.B.C, p. 

 26, should be A. grubil, and not A. ecaudata, as printed. 



" To establish the differences between these two forms 

 was the chief result obtained by Messrs. Gamble and 

 Ash worth. They have found that A. ecaudata has the 

 first gill implanted immediately behind the 16th noto- 

 podium on each side, whereas, in A. grubil, the first pair 

 of gills occurs behind the 12th notopodia ; that the 

 nephridia open on segments 5 — 17 inclusive, in A. ecau- 

 data, while in A. grubil there are only five pairs of these 

 organs opening on segments 5 — 9 ; that, in the former 

 species, the gonads are massive and compact ; in the 

 latter, diffuse and floating freely during maturation. 



" The anatomy of Johnston's A. ecaudata has hitherto 

 remained unknown. Our researches have shewn it to be 

 by far the most interesting member of the genus, in that 

 it possesses thirteen pairs of nephridia, the first of which 

 opens on the 5th chsetigerous segment, and the last on the 

 17th, or the second of the gill-bearing segments. Hitherto 

 it has been supposed that the six pairs of nephridia of 

 A. marina were typical for the genus both in number 

 and in form. It now appears, however, that the nephridia 

 of the true lug-worms are reduced in number, as com- 

 pared with the similar organs found in A. ecaudata, and 

 that the relation of these nephridia to the gonads, is 

 of a more intimate and less transient character than is 

 usually supposed to be the case, and though different 

 in detail, is essentially similar in plan, in these two 

 species. The characters by which A. ecaudata may be 

 recognised are — the presence of the first pair of gills 



