214 Bibliography. 
each pass through their successive transformations. The formation of 
cellules and their transformations into tissues and organs, form one of 
the most prominent topics treated of in this work, and it will be obvious 
to those who have paid attention to the subject, that the author’s views 
with regard to these changes, vary somewhat from those of Schwan, 
Valertin, and others, which at the present day are the most generally 
accepted. It is well known that the researches of Mirbel and Schlei- 
den, have proved that all the organs and parts of plants are originally 
composed of simple cellules; and Schwan, in making similar research- 
es with regard to animals, has been led to the conclusion, ‘ that in their 
primitive state, all the tissues are composed of cellules, and that the 
elements of all the organs, whatever their form, are also generated 
rom them.” The researches of Vogt confirm these results, but as re- 
gards the formation of the cellules themselves, he entertains different 
views. Schwan maintains that the nuclei and nucleoli are primary, 
and the germinating vesicle, secondary formations ; whereas, according 
to Vogt, the vesicle is in nearly all cases formed first, and the nuclei 
and nucleoli subsequently. In the cellules from which the epidermis, 
black pigment and intestinal canal are formed, no nucleoli make their 
appearance, until a comparatively advanced period. The nuclei are 
much more generally found than the preceding, a very few cellules be- 
ing destitute of them but these he thinks are’ as clearly secondary 
formations, since they cannot be recognized until some days have 
elapsed. With regard to the truth of the author’s views, as respects 
this and some other subjects treated of, it will be impossible to form a 
correct estimate, without going over the same ground and repeating 
his experiments. Setting aside, however, the controverted points, we 
think it will be readily admitted that his observations form an exceed- 
ingly valuable addition to the science of embryology, and the labor and 
industry with which these observations have been conducted, justify us 
in forming a high estimate of the results of his future’ researches. 
Agreeable to the plan adopted by M. Agassiz, this livraison will be 
followed by another, by the same naturalist, on the anatomical structure 
of the Salmonide. : 
2. Hooker’s Icones Plantarum; or Figures, with brief descriptive 
characters and remarks, of new or rare Plants, selected from the au- 
thor’s Herbarium. New Series, Vol. I, 1842; and Vol. II, part 1, Jan- 
SATY > 1843. (8vo., plates 401-550.) London: H. Bailliére—We du- 
ly informed our readers, (Vol. xiii, p. 189,) that the new series of this 
low-priced and very valuable work. was to be continued regularly as @ 
quarterly publication. Three numbers of the continuation have n0W 
reached us ;. which are principally devoted to the illustration of the rar- 
