STUDIES ON EARTHWORMS. 269 
given by Mr. Beddard. The ventral sete in the posterior 
region of the body are ‘52 mm. long, and have a strongly curved 
embedded portion whilst the free end is only slightly curved ; 
there is the usual thickening in the middle region (Pl. XVI, 
fig. 29). The lateral setz are three quarters this size, ‘4: mm. 
long, and I found it impossible to extract them: it is only by 
means of sections or by teasing up a piece of body wall that 
one can see them, although by means of a lens their pits can be 
seen superficially. 
In the anterior region the ventral setz are rather longer, and 
differ in shape: the thickened region, usually about the middle 
in the ordinary setz, is here just below the free end, giving 
the appearance of a spear-head to the seta. (Pl. XVI, fig. 28). 
The free ends in many cases were much worn. 
External Apertures.—The mouth is nearly terminal, 
being overlapped by the small prostomium; it is large and 
circular, and the surrounding “buccal” somite seems to 
be able to be used as a sucker, from’ what I saw of it when 
the animal was alive. 
The anus is a sub-terminal, horizontal slit. 
The dorsal pores are absent ; I could see none either by 
means of a lens, or in a series of transverse sections through 
the posterior region of the body. 
The nephridiopores are very evident (Pl. XV, fig. 1). 
Each appears as a longitudinal depression in a line with the 
lateral setze. Since the width of a pore is as great as the 
space between the two sete forming the lateral couple, it is 
difficult to say whether they are in a line with the upper or 
lower setaof a couple. Thus they differ in position from those 
in Lumbricus, where they are in a line with the ventral setz. 
Each nephridiopore (ne. 0.) occupies the anterior edge of the 
first annulus of a somite, and it was by counting the number 
of annuli between the pores that I was able to ascertain the 
number of anuuli that go to make up a somite. 
The first nephridiopore is in the fourth annulus, and as there 
is never a nephridium in the first somite I regard this annulus 
as the commencement of the second somite. Thus somite 
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