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BULLETIN OF THE BUREAU OP FISHERIES 



Fin rays (DR, PR, VR, AR). — In the dorsal and anal fins the first one or two 

 unbranched rays are poorly developed. Only when their length approached three- 

 fourths that of the longest ray of the fin were they included in the count. Every 

 ray in the pectoral and ventral fins was counted. 



Vertebra. — The flesh was removed from one entire side of the fish until the 

 vertebral column was plainly exposed. Every vertebra was counted, including the 

 last of the upturned ones at the base of the caudal fin. 



Pyloric cxca. — The gut was removed and each csecum picked off with the for- 

 ceps. The count includes the caeca on the small intestine. 



Branchiostegal rays (Br). — Every ray in the membrane was counted. 



Miscellaneous Terms 



Body. — Where the term "body" is used in the text it is meant to designate the 

 body of the fish exclusive of the head. 



Pearl organs. — These excrescences of the epidermis are developed only during 

 the breeding season, often only in males. They attain their greatest development in 

 the coregonids on the scales of the sides but also are evident on those of the other 

 surfaces and usually on the head and fins. 



SYSTEMATIC TREATMENT 



In many groups of animals most of the species have been described already, 

 and systematists, in turning their attention to the analysis of these species, have 

 found that a species group is by no means so homogeneous as was supposed originally. 

 It appears that most animals and their offspring, either from incapacity to do other- 

 wise or from choice, breed in an area that, in comparison with the range of their 

 species, is very restricted. Regional differences in structure or habit, associated with 

 conditions of the environment, may be developed, therefore, and the animals of a 

 species in certain localities may be distinguished by peculiar features. In the case 

 of land animals it has been current practice to call these geographic races or varie- 

 ties subspecies. Some species appear to be more plastic than others, and the num- 

 ber of subspecies that has been recognized in some species groups has reached a con- 

 fusing total. Though it has been apparent that in certain widely separated regions 

 the same sort of changes often were exhibited by the species of an animal group (for 

 example, the coastal areas of British Columbia and Labrador are inhabited by several 

 races of widely distributed birds that are darker than their relatives of the same 

 species elsewhere), the changes are not identical throughout; and in general it is 

 not known to happen commonly that two intraspecific groups of animals alike in 

 their external features occur in geographically separated areas. In other words, the 

 range of a terrestrial subspecies is considered continuous, and a subspecific name has 

 a geographic connotation. 



As a matter of fact, probably no species has a strictly continuous range. Its 

 distribution depends on the distribution of suitable areas within the broad limits 

 of its range. Thus, animals that inhabit swamps are found only wheie in their range 

 swamps occur, and one such swamp may be separated by a vast distance from another. 



To be sure, in mountainous areas, where altitude alters the natural effects of 

 latitude, and in insular areas like habitats may be markedly disconnected and the 



