PREFACE. ix 



to he brought to a dose before its size amounted to wiiat it should bo ; iiut in the sue- 

 ceeding vohunes full eonipcnsation will be made fur this, and measures taken to bring 

 tliem forward with more promptitude. 



With reference to tiie future progress of Zoiilogy in Ihis coimtry, it is particularly 

 desirable that investigators should not allow themselves to be carried away by the almost 

 inexhaustible diversity of species, so as to confme their efforts to describing merely what 

 is new, for however desirable it may be that all our species should be correctly named, 

 described, and (h'jineated, such labors are, in fact, only the preliminary steps towards deeper 

 and more piiilosophical studies; and the sooner attention is turned to the mode of 

 life of all our animals, to their geographical distribution, their natural affinities, their 

 internal structure, their embryonic growth, and to the study of fossil remains, the sooner 

 will the investigations of American naturalists contribute largely to the real advancement 

 of science, and the investigators themselves acquire an independent standing among scien- 

 tific men. I am well aware, while writing this, that there are already many who pursue 

 the study in that truly scientific spirit which has brought Natural History to its present 

 prosperous state ; my remarks, therefore, do not a|)ply to these noble devotees of truth. 

 But 1 know equally well, that there are too many who fancy that describing a new 

 species, and hurrying to the press a hasty and mostly insulTicient diagnosis, is a real 

 scientific achievement. These I would warn from the deceptive path, adding, that a long 

 e.xperience has taught me that nothing was ever lost to an investigator by covering, as 

 far as possiijle, the whole ground of any subject of inquiry; and that, though at times a 

 subject may seem to have lost , some of its value for being less novel, it gem-rally gains 

 tenfold in scientific importance by being presented in the fullest light of all its natural 

 relations. It is chielly this conviction which has induced me to keep to myself for so 

 many years the results of my investigations in this country; and if, in the course of this 

 j)ublication. 1 am occasionally compelled to offer fragmentary information upon many parts 

 of my subject, it is simply because the time has come with me when I must publish what 

 I have been able to observe, if T would publish at all. 



Scandinavia, Germany, and Franco afford us striking examples of the new impulse 

 science has received, in consequence of the gradual exhaustion of the field atlbrded them for 

 descriptive Zoology. As soon as most of the species of these countries luul been described, 

 after LinnuMis had begun to register systematically the whole animal kingdom, those who 

 were denied the opportunity of visiting foreign countries, or of receiving large supplies of 

 new species from distant lands, applied themselves to the investigation of the iutenuil 

 structure of the animals already described, and to the study of their habits, their metamor- 

 phoses, tlu'ir embryonic growth, etc. Never did Zoology receive a more important iiupulse than 

 at the time when (ieiinan students began to trace with untiring zeal the earliest development 

 of all the classes of the animal kingdom, and some Scandiuaviiui observers pointed out the 



B 



