PERCENTILE PROPORTIONS OF LAKE AND ATLANTIC SALMONS. 131 



Again the proportions of some length-classes of lake salmon are the same as those of 

 the parr stages of Atlantic salmon. Then again proportions of length classes of lake 

 salmon correspond to no proportion of the Atlantic salmon. When, as is to be seen, the 

 proportion of length classes of lake salmon are exactly the same as that of the breeding 

 Atlantic salmon and the parr also, the fact is probably attributable to the modification 

 of dimension which has taken place incident to the development of the breeding con- 

 dition of the Atlantic salmon, which raises or reduces, as the case may be the proportion 

 to the level of the parr. In some such instances it is probable that proportion of the lake 

 salmon is to be considered with only one or the other of the stages of Atlantic salmon, 

 i.e., either with the parr or breeding fish; most Ukely it is with parr. 



Some of the relations of length classes, as indicated by the averages, are shown in a 

 different way and by different length-classes of lake salihon of the three localitj' groups. 

 This fact points to possible differences among them as well as between the lake salmon 

 and Atlantic salmon. These variations of relationship of the proportions as shown by the 

 different length classes of lake and Atlantic salmon in tables 21-22, and of a few other 

 length-classes of Atlantic salmon not included in the tables, are as follows : 



Inter orbital. — Only breeding lake salmon are not represented in the averages of 

 proportions of the length classes of Atlantic salmon. All of the breeding lake salmon, 

 excepting the 17.6-inch Grand Lake male, have the same proportion, which is inter- 

 mediate between the proportions of the smaller and larger Atlantic salmon. Thus the 

 breeding lake salmon have lower average proportions for the interorbital than in the 

 breeding Atlantic salmon. On the other hand the smaller length-classes of non-breeding 

 lake salmon have higher averages than the smaller length-classes of Atlantic salmon. 

 In general, then, regardless of sex the average of proportions of interorbital in the lake 

 salmon decrease from the smaller to the larger length-classes, while in the Atlantic 

 salmon they increase. This fact indicates different trends of changes of proportions in 

 the lake salmon and Atlantic salmon. 



Eye. — Again it is only by the breeding lake salmon that the Atlantic salmon lacks 

 representation. The proportions of the eye in both lake and Atlantic salmon decrease 

 with increase in length of the fish. All of the proportions of the lake salmon fall within 

 the range of the proportions of the Atlantic salmon. The only difference is that in the 

 lake salmon the average is somewhat higher than in the Atlantic salmon. The females 

 show a greater difference in this respect than do the Atlantic salmon. The 13.2-inch 

 female Presumpscot salmon has exactly the same proportion as the 13.9-inch male 

 Atlantic salmon. 



Snout. — Only certain length classes of the Presumpscot and Sebago salmon are not 

 represented in the proportions of the Atlantic salmon and these are not restricted to 

 breeding fish. The proportions of the lake sahnon are lower than those of the Atlantic 

 salmon excepting that the 25.5-inch breeding male Sebago fish is three per cent higher 

 than that of the 28.3-inch breeding male Atlantic salmon. The proportions of both male 

 and female Atlantic salmon increase from the smaller to the larger length-classes as do 

 those of the male lake salmon, but the female lake salmon are irregular in that respect. 



The 13.2-inch Presumpscot female and the 16.5-inch Sebago female are equal to the 



