136 Bibliographical Notices. 



No one who regards the modem progress of zoology can fail to 

 agree with the view here expressed ; but how does it harmonize with 

 Prof. Ehrenberg's main and fundamental doctrine, that organization 

 has no relation to size, and that the Infusoria have all the organs 

 which characterize the higher animal ? 



Indeed, while we can conscientiously recommend the present work 

 as a very useful assistant to those who are working for themselves, 

 we must caution our readers against the very unphilosophical sub- 

 servience to the authority of a name which it too often exhibits. 

 Thus, after a discussion of the polygastric theory of Ehrenberg, we 

 find it said of subsequent observers — 



" With Van der Hoeven, all coincide in denying the existence of an 

 inclosing wall to the vesicles, and of an intercommunicating tube be- 

 tween them ; and all assert the ever- varying number and disposition, 

 as well as the movements (even rotatory) of these supposed stomachs." 

 And yet we are told further on — 



" From the preceding conflicting opinions and observations no 

 satisfactory deduction can be made ; Ehrenberg's opinions, however, 

 are entitled to great respect, although the theory of a polygastric 

 structure may not admit of demonstration." 



We have every respect for Prof. Ehrenberg, but we are really at a 

 loss to understand why his opinions, if they be " incapable of demon- 

 stration," are more " entitled to great respect" than those of any one 

 else, especially when these opinions are at variance with those of an 

 unanimous host of at least equally competent observers. 



Authoritative assertion in science, it is well to remember, is not evi- 

 dence ; it only affords a presumption, better or worse founded ac- 

 cording to the real value of your authority, that evidence may exist. 

 Great authority may be a good ground for a temporary suspension of 

 judgement when opposed to less authority, but it is valueless when 

 opposed to good evidence. 



A great authority, whose " opinions are incapable of demonstra- 

 tion," is a sort of scientific balloon, brilliant to look at and much 

 gaped at of the multitude ; but containing nothing but gas and sand, 

 and liable to come down with a crash at the touch of the first critical 

 penknife. 



A Synopsis of the Family of Naiades. By Isaac Lea. Third edition, 

 greatly enlarged and improved. Philadelphia, 1852. 4to. 



By the title of this work we might be led to suppose it would afford 

 the conchologist the means of determining the species of this very 

 interesting family of freshwater bivalve shells, or at least give a re- 

 ference to the books where the species are figured and described, and 

 the countries they inhabit. Unfortunately the author has not thought 

 this desirable. The work simply consists of a list of 7^7 species, each 

 followed by the names by which other authors have described it, 

 accompanied by an abbreviation of the name of the author. 



Then follows a list of the species of each subgenus, arranged in 

 alphabetical order, under Europe, Asia, Africa, North and South 

 America, and New Holland, as they happen to inhabit. 



