198 HYATT, 



the different systems of organs, from their lowest to their 

 highest states. 



The laws, also, according to which the changes, or dif- 

 ferences in the parts, take place, are better illustrated by 

 such a tabular view, than by any other method. 



The manner commonly pursued of describing the mi- 

 nute differences between species, or genera, and of simply 

 generalizing with regard to their anatomical peculiarities, is 

 very unsatisfactory. It does not afford the means for com- 

 paring the anatomical composition of the parts of the in- 

 dividual in each species, or genus, which is necessary to a 

 complete understanding of the whole, and the differences 

 are sought for and described, to the neglect of the agree- 

 ments, that are either passed by, or only casually noticed 

 in the descriptions of the larger divisions. Such errors are 

 avoided by the use of analytical tables, which, besides the 

 advantages before described, set forth the similarities as 

 prominently, as the differences. We thus never lose sight 

 of the initial points of the structure, while the differences, 

 or changes, from t'me to time appearing, stand out even 

 more vividly against the common background of similari- 

 ties. 



It is far from my intention to underrate the labors of 

 naturalists who devote themselves to the discovery and 

 publication of new forms; their labors are essential to 

 the progress of science. The ordinary mode, however, of 

 prosecuting these investigations is, perhaps, too disconnect- 

 ed, species being habitually regarded in the light of isola- 

 ted creations, rather, than as allieol to others by the larger 

 number of their essential characters. This engenders a 

 habit of always looking for differences, and overlooking 

 agreements, which the study of series of species, or even 

 of series of individuals would correct. 



The facts published in these ''Observations" have been 

 verified by my own experience, with the single exception 

 of the spermatozoa. These I have not yet seen, my obser- 

 vations having been made, for three successive seasons, 

 principally during the fall and winter months. 



The questions involved in the body of the paper, and 

 the difficulties to be overcome in obtaining living Euro- 

 pean specimens have obliged me to quote extensively from 



