262 THE VARIATION, RACES AND MIGRATIONS OF THE MACKEREL. 



fundamental relations to the myotomes ; they are not only parallel and 

 unbroken, but also geniculate in shape. Secondary regularity is caused 

 by the anastomosis of portions of the pigment streaks of neighbouring 

 myotomes in such a regularly repeated manner as to produce an equally 

 marked parallelism of arrangement, coupled with a partial or complete 

 loss of the typical geniculate curvature and relation to the myotomes. 

 Thus a parallel series of vertical, or oblique, bars is frequently exhibited; 

 and in such a case each bar upon dissection has been found to cross 

 several adjacent myotomes, instead of following any individual myotome 

 along its course. By grouping those two types of arrangement under 

 the same head "regular," I was unwittingly uniting things which 

 should have been poles asunder. 



On discovering this error, I proceeded to record the general shape 

 of the bars in addition to their degree of regularity ; but it would 

 be unprofitable on the present occasion to give a general account of 

 these later observations, owing to the fact that the majority of the 

 fish examined during the autumn of 1897, including the bulk of 

 the fish from Kinsale, would have to be omitted from consideration. 



It has, however, been asserted by Donovan {fide Day, British Fishes, 

 Vol. I. p. 84) that the sexes can be distinguished by the shape of the 

 bars, these being " straight " in the male and " undulated " in the 

 female. As my observations are amply sufificient to test the accuracy 

 of this statement, I give some figures bearing on the question. As 

 the term "undulated" is somewhat ambiguous, and may be held to 

 apply to the angular > shaped, or geniculate, bars, as well as to 

 those of a more truly wavy, or convoluted type, I have determined 

 the proportion of the sexes exhibiting each of these characters, in 

 addition to the proportion exhibiting straight or vertical bars. To 

 avoid all doubt, I have eliminated all cases except those in which 

 the bulk of the bars could be definitely described as either geniculate, 

 wavy, or straight. 



The results are shown in the following table : — 



Table VI., shoiving Shape of Bars in relation to Sex. 



