1896.] I'HOJI TUB SANDWICH ISLANDS. 199 



constant up to the end of the body. The formula " will read 

 thus : — 



Segment I. V. XII. XVI. 



No. of seta? .... 23 31 43 46 



but on some segments quite close to the tail I counted as many as 

 49 setfe. The size of the setie varies on different segments and on 

 different parts of the same segment. The setse on either side of 

 the nerve-cord, as is the case with other species (e. g. Periclia;ta 

 JiouUeti), are larger than those more laterally placed. This 

 difFeience commences to be well marlted in the third setigerous 

 segment, anterior to which, it may be observed, is no ventral nerve- 

 cord, but the circumoesophageal commissures. From the third 

 setigerous segment to the sixth (inclusive) there is this marked 

 difference between a few ventral seta) — particularly the ventral- 

 most seta — on either side of the nerve-cord and the rest of the setre 

 of the segment. On the tenth segment all the setse are very 

 much smaller than on the preceding segments ^, and those on 

 either side of the ventral nerve-cord are not larger. On the 

 eleventh segment the seta) again are larger, aud there is a slight 

 difference in size between tlie ventralmost two or three setse and 

 the rest, but not nearly so marked as on segments iv.-vii. 



The cliteilum is, as has been already mentioned, entirely witnout 

 setiB ; but no doubt in the immature worm they are present. In 

 any case the special longitudinal muscles of the setoe were quite 

 obvions in the mature worm. At the hinder end of the body the 

 selas are larger than those of some of the anterior segments — a 

 difference which may have to do with the habit (so general 

 among earthworms, at least of this country) of lying outside the 

 burrow with the tail only concealed within. 



The first septum lies between segments v./vi. The septum 

 between viii./ix. is missing, as is nearly universally the case with 

 Perichwta. The septum between ix./x. is largely defective, though 

 not absent ; it consists chiefly of a strong muscular band on 

 each side, which is attached to the insertion of the next following 

 septum. Septa v./viii., x./xiii. are moderately thickened. 



lu the hinder part of the body were paired masses of coelomic 

 cells, attached on either side of the dorsal blood-vessel, such as I 

 have described in PericJtcnta. They were full of Gregarines. 



The pliaryiuv is beset with numerous salivary glands, which 

 extend back as far as the sixth segment. The gizzard is globular, 

 not in any way elongated. 



The last heart is in segment xiii. 



The sperm-sacs are in segments xi., xii. ; there are, as usual, two 

 pairs of sperm-duct funnels. 



• This is a little different from tlio segments originally selected ("On some 

 Species of the Genus Pcrichafa," V.Z.a. 1892, p. U'7); but as the number 

 culminates at xvi. I hiiTo thought it well to emphasize the fact by tlie formula. 



" In relattou to this fact, it is inleresiing to observe that in Ferichceta 

 caducichmta (Beuham, Ann. & Mag. Nat. Hist. ser. 6, xvi. p. 47, 1895) the setm 

 upon this segment are absent. 



