S. A. Arendsen Hein 253 



a priori considerations about the genotypic value of these deviations ; 

 in other words I did not prejudge the possibility whether some devia- 

 tion should be regarded as a pathological disturbance in the develop- 

 ment or as a reaction of a changed complex of gens. Looking back I do 

 not regret having taken this point of view, in spite of the extension of 

 the labour it entailed. For not seldom were the results contrary to 

 expectation, often even when I had to deal with variations of taxonomic 

 value. 



The following list gives a survey of the most important deviations 

 which were observed and tried as to their hereditary character. When 

 nothing is mentioned about the latter it means that either no positive 

 result has been obtained, or that the experiments are not yet closed. 

 The hereditable deviations will be treated with full data in subsequent 

 papers. 



a. The Eyes. 



No. 1 a. The normal colour of the eyes is intensely black. In very 

 rare cases they are cream-white, here spoken of as yellow, and when 

 observed for the first time, this condition was mostly found in cT beetles. 

 On one occasion it was noticed in $ individuals in a population bought 

 in the trade. The yellow eye-colour is sex-limited in its descent, follow- 

 ing the rule known for colour-blindness in man, and exemplified by the 

 many recessive sex-linked characters investigated by Morgan in Droso- 

 phila. 



Black-eyed $ x yellow-eyed (/" gives all ^i black-eyed, $s and cTs 

 alike. In F2 from this cross, yellow-eyed ^/'s reappear. 



Yellow-eyed $ x black-eyed cT gives the $s black-eyed and the c/'s 

 yellow -eyed ; and in F^ from this cross all four forms are produced. The 

 numbers will be given when sufficient data have been obtained, and, 

 together with certain aberrations which have been met with, will be 

 discussed in a subsequent paper. 



No. 1 b. In other cases the eye colour may be red. This anomaly 

 appears not to be sex-limited. 



No. 2. One of the eyes may be rudimentary without the other organs 

 on that side of the head being influenced by this. 



No. 3. One of the eyes may be entirely wanting. In the few cases 

 that occurred the right or left eye was absent. This fact was associated 

 with a partial development of the right or left half of the head; the 

 right antenna or that part of the clypeus overarching the basis of the 

 antennae was lacking also. 



