1899] ROCK-ANALYSIS 445 
rocks in which their presence would hardly have been suspected, and which in 
ordinary analyses would have been unsought and overlooked. ‘The translation 
contains some additional remarks upon and references to the later observations 
of Dr. Hillebrand, and on p. 33, a woodcut, not given in the original Bulletin, 
illustrates the construction of a modified form of Gooch’s apparatus, as employed 
in the U.S. Survey laboratory for the determination of combined water. The 
translation is well printed and has an index, but although it is a most useful 
and convenient publication, the original Bulletin No. 148, with its well-tabulated 
analyses, will probably be more frequently consulted in this country than 
Dr. Zschimmer’s careful translation. 
MESOZOA AND SPONGES. 
Traité de Zoologie Concrete. Lecons professées a la Sorbonne. Tome ii. 
1"* Partie. Mésozoaires, Spongiaires. By Yves DELAGE and EpGARD 
HEROUARD. Pp. ix. + 244, with 15 coloured pls. and 274 figures in the 
text. Paris: Librairie C. Reinwald, Schleicher Fréres, 1899. Price 
12s. 6d. 
The new instalment of this great work sustains the high level of its pre- 
decessors in its fulness and clearness of exposition, and in its liberality of 
excellent illustrations. The first part contains the fullest connected account as 
yet published by the so-called Mesozoa, and is therefore of great interest. Four 
classes are recognised :—(1) Mesocoelia, viz. Salinella ; (2) Mesenchymia, in- 
cluding 7'reptoplax and Trichoplax ; (3) Mesogonia, comprising Dicyemiae and 
Orthonectiae ; and (4) Mesogastria, viz. Pemmatodiscus. An appendix treats 
of Physemaria, Cementaria, Pompholyxia, Kunstleria, and Siedleckia. The 
authors have conferred a great boon on zoology, in bringing together the avail- 
able information in regard to these obscure creatures which are as interesting 
as they are puzzling. 
The second part deals with the sponges, to our knowledge of which Prof. 
Delage has made some notable contributions. As was expected, there is a care- 
ful discussion of the affinities of the class, in which Delage’s own views are 
naturally followed, though the diversity of opinion is duly recognised. The 
classification adopted is as follows :—I. Calcaria, including Homocoelida and 
Heterocoelida; IL. Incalearia, including Triaxonia (Hexactinellida and Hexa- 
ceratida) and Demospongiae (Tetractinellida, Monaxonida, and Monoceratida). 
An appendix deals with the doubtful Abyssospongea, which probably do not 
deserve the name. A zoological treatise on different lines may well be con- 
ceived, but it will be hard to excel this one in clearness and fulness, or in beauty 
of illustration. 
ELEMENTS OF VERTEBRATE EMBRYOLOGY. 
Die Elemente der Entwickelungslehre des Menschen und der Wirbelthiere. 
Anleitung und Repetitorium fiir Studierende und Aerzte. By Dr. 
Oscar HErRtwIG, Director of the Anatomical-Biological Institute of the - 
University of Berlin. 8vo, pp. vi. +406, with 332 figs. Jena: 
Gustav Fischer, 1899 [dated 1900]. Price 7.50 marks, 8.50 bound. 
In twelve years Prof. Hertwig’s well-known Lehrbuch has passed through 
six editions, and has been translated into English, French, Italian, and Russian ; 
and no one who has used it, whether as student or teacher, will wonder at its 
great success. It is a model of lucidity, it is well illustrated, it is flavoured 
with the salt of general ideas, and it is full of suggestion. 
But as he worked at the later editions, Prof. Hertwig began to feel that it 
was impossible to cater for two sets of appetite. The expert wished for more 
30—wnat. sc.—voL. xv. No. 94. 
