L888.] of Curves and of Surfaces. Od 
A ee is Ra it in ie 
keke, ras x kb, aC : 7 lyk? a ae Tigh? 
k, es h, #4 i L, - e 
ee 
le Z i ae) i 2 ‘bs: 
bib, o & 7 ne aoe a at 2D ahs 
If we write de =iF 4) jek 2 | 
we shall have an equation of the form do’ =p.dp.p7, where p is 
some quaternion. Combining this equation with the equation 
do=q.dp.q", we obtain 
Gir == OD dha 0 DO) °F 
and, if we write Q=qp', this equation becomes do =Q.da'. Q”. 
Utilizing a similar method to that adopted in the preceding article, 
we shall at length obtain 
b, OF | hy 2 i a ath, Om 
Ce cacsh mek neous | ae AO, oe 
Ieee eos) nen a ae 
Te i Brot 6 Gah, Gel 
June 4, 1888. 
Mr J. W. CLARK, PRESIDENT, IN THE CHAIR. 
HE. H. Grirrirus, M.A., Sidney Sussex College, was elected a 
Fellow of the Society. 
The following Exhibitions and Communications were made: 
(1) Hehibition of Steropus madidus and Earthworm. By Pro- 
fessor HUGHES. 
The author exhibited a specimen of the common earthworm 
and of the larva of Steropus madidus which was attacking it. 
