It has always been my opinion that the true science of zoology is entirely based upon an exact and detailed knowledge of those types in nature to which we are in the habit of applying the term species and conspecies and upon our acquaintance both with the constant varieties and with the individual variations of the species. Indeed the science of zoology lays claim to its full dignity only when it is considered as a subdivision of the immense domain of physical geography. These considerations naturally lead to the conclusion that zoological science can only be thoroughly studied in those central collections which contain the greatest possible number of species. Each of these species must there be represented by complete series of perfect specimens, illustrative of all the different phenomena consequent upon difference in age or sex of the individuals, upon difference in season, locality, variety, variation, etc. ¹)