XXXVm PROCEEDINGS OP THE 



individual organisms, (2) of preserved specimens, (3) of pictorial 

 delineations, and (4) of written descriptions. Each of these sources 

 of information has its special advantages, but each is attended by 

 some special deficiencies to be supplied by one or more of the others. 



1. The study of living individuals in their natural state is without 

 doubt the most satisfactory ; but very few such individuals can be 

 simultaneously observed, for the purpose of comparison, and no one 

 individual at any one moment can supply the whole of the data 

 required, relating even to that individual. Some additional facilities 

 in these respects are given by the maintenance of collections of 

 living animals and plants, particularly ixseful in affording the means 

 of continuous observation during the various phases of the life of 

 one and the same individual, and sometimes through successive 

 generations, or in facilitating the internal examination of organisms 

 immediately after death, when the great physiological changes con- 

 sequent upon death have only commenced. But there are drawbacks 

 and difiiculties to be overcome, as well as a few special sources of 

 error to be guarded against ; and in this respect, as well as in the 

 progress recently made in their application to science, there is a 

 marked difference between zoological and botanical living collections, 

 or so-called gardens. 



The great drawback to living collections, especially zoological, is 

 their necessary incompleteness. At the best it is individuals only, 

 not species, and in. a few cases genera, that are exposed to observa- 

 tion. Genera, indeed, can always be better represented than species, 

 for a few species bear a much larger proportion to the total number 

 contained in a genus than a few individuals to the total number 

 which a species contains. "Whole classes are entirely wanting in 

 zoological gardens, which are usually limited to Yertebrata. Of late 

 years means have been found to include a few aquatic animals of the 

 lower orders ; but insects, for instance, those animals which exercise 

 the greatest influence on the general economy of nature, the obser- 

 vation of whose life and transformations is every day acquiring 

 greater importance, are whoUy unrepresented in zoological gardens. 

 The shortness of duration of their individual lives, their enormous 

 powers of propagation, the different mediums in which they pass the 

 different stages of their existence, will long be obstacles to the 

 formation of living entomological collections on any thing like a 

 satisfactory scale. The cost, also, of the formation and maintenance 

 of living collections is very much greater in the case of animals than 

 of plants ; but, on the other hand, zoologists have the advantage 

 of the attractiveness of their menageries to the general unscientific 



