142 DR. Vl. B. BENHAM ON [Feb. 16, 



out that the numbering of the somites, as it stands in my description, 

 requires some alteration, and Beddard *^has hkewise made certain 

 corrections in regard to the interpretation of certain organs, which 

 have become necessary from the advance in our knowledge of the 

 anatomy of the group^. I here give a figure (Plate VIII. fig. 8) of 

 the anterior end of M. beddardi, in illustration of my remarks on 

 the alteration of numbering of this somite. 



MicrocAceta papillata has a length of 10 inches and a breadth 

 of half an inch ; it is thus smaller than either of the two previously 

 known species. As to its colour, I am unable to speak, for, as is 

 so generally the case, it has evidently been considerably changed by 

 the spirit. 



The prostomium (Plate VII. fig. 5) is, as in M. beddardi, broad and 

 marked by longitudinal grooves, which extend into the first somite 

 {cf. Plate VII. fig. 6, representing 31. belli) ; this somite is similarly 

 grooved on the ventral surface. The following somites are hi- or 

 tri-annulated, but the grooves between the annuli are in some cases 

 almost as marked as those between the somites, so much so, indeed, 

 that in fixing the position of the various external characters I at first 

 reckoned the annuli as somites. The first three somites are not 

 annulated ; the fourth to the ninth inclusive are bi-annulated 

 (a, b), the grooves between the annuli being very deep ; posteriorly 

 the somites are not so noticeably annulated. This same well-marked 

 annulation of the somites exists, as I have pointed out and figured, 

 in M. rappi. 



The chcetce, however, serve to define the somites, and, as in the 

 other two species, are iu four couples per somite, the individuals of a 

 couple being close together ; the outer couple is quite lateral in 

 position, being about midway between the dorsal and ventral median 

 lines ; whilst the inner couples are latero-ventral. The interspace 

 between the outer and inner couples is about equal to the space 

 between the two inner couples. The chsetse themselves are very 

 small, and in the anterior somites, indeed, I had to make use of 

 Zeiss's B, as a hand-lens, in order to see them ; they commence in 

 somite iii. It might be suggested that the first somite is biannulate, 

 but in M. belli (Plate VII. fig. 6) the chsetse occur in the second 

 somite, which is in other respects similar- to the second ring of the 

 present species. The four species exhibit an interesting series of 

 stages in " cephalization." In M. belli the first and second somites 

 are distinct, the chsetse being present on the latter. In M. beddardi 

 these somites are not distinctly marked off from one another (Plate 

 VIII. fig. 8), and the apparent first somite carries clisetae in its 

 hinder part ; in M. papillata, though the somites are distinct, the 

 chsetse are absent on the second : iu M. rappi the two somites are 

 with difficulty distinguishable from one another ; the first annulus 



^ " The Olassification and DiBtribution of Earthworms," Proc. Eoy. Phys Soo 

 Edinb. X. pp. 242, 243. 



* Eosa pointe out this neceEsarv correction iu the paper just referred to, on 

 p. 384. 



