10 MUSEUM OF COMPARATIVE ZOOLOGY. [Jan. 



random has less value than collections made systematically. I 

 have therefore drawn up short instructions for collectors, which 

 I have caused to be printed and circulated very extensively ; 

 and I have no doubt the result will be felt in the course of the 

 present year in the improved condition of the specimens received. 

 The Superintendent of the U. S. Coast Survey, Dr. A. D. Bache, 

 is conferring a permanent benefit upon the Museum, by direct- 

 ing the light-house keepers, stationed in favorable localities, to 

 devote their leisure to the picking up of specimens in conformity 

 with the instructions sent to them. Among these directions is a 

 request to pay particular attention to young animals, as the study 

 of the young has been thus far too much, if not altogether 

 neglected. During the present year the collection of young 

 animals has been very largely increased, chiefly through the 

 exertions of the gentlemen directly connected with the Museum ; 

 but in proportion as the importance of such collections begins 

 to be more extensively understood, we may look for additions 

 of this kind from other parts of the world. The scientific 

 returns for these efforts are near at hand, as improvements in 

 the classification of adult animals are daily suggested in conse- 

 quence of comparisons with young of other families. I have 

 myself been richly rewarded for my attention to this subject, by 

 the discovery, at once verified in the principal families of the 

 class, that fishes undergo as varied and as extensive metamor- 

 phoses, after hatching from the egg, as the Batrachians do. 

 The types in which these facts have been ascertained are the 

 Lophioids, the Labroids, the Cyprinodonts, the Atherinoids, the 

 Cottoids, the Blennioids, the Percoids, the Cyprinoids, the 

 Siluroids, the Esocids, &c. 



Another interesting result incidentally arrived at, during 

 these investigations, was the possibility of determining at once, 

 under certain circumstances, the age of slow-growing animals 

 which could not otherwise be ascertained. 



Every-body is forcibly impressed with the longevity of the 

 trees of our forest, when he sees how little the oak, or the 

 maple, or the elm in his father's garden has been enlarged since 

 his childhood. But when we see chickens growing to their full 

 size in a few months and our largest animals attain their 

 imposing dimensions in a few years, the impression must natu- 

 rally be general, that animals rapidly complete their growth, to 



