282 



may be the bond of your connubial happiness is our most sincere 

 wish, and also that Divine Providence may long, very Ions:, presence 

 Your Royal Highness's life, in possession of every blessing, both as 

 a husband and as a father." 



The Society then adjourned over the Christmas recess, to meet 

 again on the 7th of Januaiy next. 



Januar}' 7, 1841. 



Sir JOHN W. LUBBOCK, Bart., V.P. and Treas., in the Chair. 



Julius Jeffreys, Esq., was balloted for and duly elected into the 

 Society. 



The following communication was read, viz. — 



" Variation of the ^Magnetic Declination, Horizontal Intensity, 

 and Inclination observed at Milan on the 2.3rd and 24th December 

 1840." Communicated by Professor Carlini, Director of the Milan 

 Obser^'atory. 



A paper was also read, entitled, " On the Chorda dorsalis." By 

 Martin Barry, M.D., F.R.S.S. L. & E. 



The author of this communication, after pointing out the similarity 

 in appearance between an object noticed by him in the mammiferous 

 ovum, and the incipient chorda dorsalis described by preceding ob- 

 sei"vers in the ova of other Yertebrata, mentions some essential dif- 

 ferences between his own observations and those of others as to the 

 nature and mode of origin of these objects, and their relation to sur- 

 rounding parts. Yon Baer, the discoverer of the chorda dorsalis, 

 describes this structure as " the axis around which the first parts of 

 the foetus form." Reichert supposes it to be that embryonic struc- 

 ture which ser^'es as a support and stay " for parts developed in 

 two halves. The author's observations induce him to believe that, 

 instead of being " the axis around which the first parts of the foetus 

 form," the incipient chorda is the last-formed row of cells, which 

 have pushed previously-formed cells farther out, and that, instead of 

 being merely " a support and stay " for parts developed in tv^o 

 halves, the incipient chorda occupies the centre out of which the 

 "two halves" originalh' proceeded as a single structure, and is it- 

 self in the course of being enlarged by the continued origin of fresh 

 substance in its most internal part. 



The author enters into a minute comparison of the objects in ques- 

 tion ; from which it appears that the incipient chorda is not, as Baer 

 supposed, developed into a globular form at the fore end, but that 

 the linear part is a process from the globular ; and that the pellucid 

 cavity contained within the latter — a part of prime importance, being 

 the main centre for the origin of new substance — is not mentioned 



