Bibliographical Notices. 383 
of the book, devoted to systematic embryology, contains a discussion 
of the mode of origin and homologies of the germinal layers, and a 
most important consideration of the nature, origin, and aflinities of 
larval forms. 
The second part of his Treatise Dr. Balfour devotes to Organogeny ; 
and in it he describes in considerable detail the origin and develop- 
ment of the various organs throughout the animal ‘kingdom, so far 
as such a treatment is possible, in the present state of our "know- 
ledge of the organogeny of the Invertebrata. The different organs 
are “classed roughly i in accordance with the germinal layers Som 
which they are principally derived. 
It has been impossible for us here to give more than a brief indi- 
cation of the mode of treatment adopted by Dr. Balfour in this most 
valuable book, which certainly ought to be upon the shelf of 
every student who wishes to understand and follow the progress of 
zoology in these modern days. The second volume, like its prede- 
cessor, is copiously illustrated with excellent wood-engravings. 
Compte Rendu des Excursions (1) aux Environs de Renaix, (2) aux 
Environs de Brucelles, (3) dans le Boulonnais, (4) dans le Qua- 
ternaire de la Vallée de la Somme. Par A. Ruror. 
(5) Sur les Restes de Mammiferes Terrestres dans les ees de 
V Eocéne de Belgique. Par A, Ruzor. 
(6) Les Terrains Tertiaires de la Belgique. Par A. Ruror et G. 
Vincent. Liége, 1879. 
Tue first four papers have appeared in the ‘ Annals’ of the Malaco- 
logical Society of Belgium, and comprise notices by M. A. Rutot of 
excursions to some localities of geological interest. Thus the Mont 
de la Musique, in the environs of Renaix, afforded sections of the 
Lower and Upper Eocene deposits, in which a different interpretation 
of the strata there exposed is assigned from that given by M. Dumont. 
The Brussels excursion extended over three days, during which the 
most interesting exposures of the Middle and Upper Eocene and 
superficial deposits around the city were examined. The extra- 
ordinary meeting of the French Geological Society was held at 
Boulogne in 1880; and M. Rutot gives a short account of the geo- 
logical character of the Secondary rocks of the coast-section and of 
the Paleozoic rocks of the interior. The Quaternary strata of the 
vicinity of Abbeville, their characters and fossil contents, form the 
subject of the fourth paper. In the fifth paper M. Rutot, after 
noticing the oscillations of the Eocene series and the continental 
periods resulting therefrom, describes the stratigraphical position 
of the terrestrial Mammalia found in the Kocene strata of 
Belgium. 
The memoir by MM. A. Rutot and G. Vincent is intended to 
comprise a general but concise account of what is known (to 1879) 
