Page:Proceedings of the Royal Society of London Vol 4.djvu/308

Rh 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 two 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 question; 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