364 Eye-Colour in Gammarus 



difference in the percentage of spotted young in families whose Albino 

 parent was spotted and in those in which the Albino parent was un- 

 spotted. 



When Albino was mated with Albino the percentage of spotted 

 young in the families was very much higher, from 43 °/^ to 86*4 °/„. 

 There seems no significant difference in the percentage between families 

 of spotted and unspotted parents. 



A pure spotted strain was never obtained. 



V. Spots with the No-white Mutation. 



As already explained the No-whites appear to be of two different 

 kinds, (a) those which we call Pure No-whites, which arise suddenly 

 and independently in the different stocks, and (6) those which possess at 

 least the normal quantity of white pigment at the time of hatching, but 

 gradually lose it with growth, until they eventually become completely 

 No-white. 



(a) Pure No-whites. Many of the animals with pure No-white 

 eyes, arising suddenly from normal parents, are found to carry spots of 

 white pigment on the head and 1st segment similar to those described 

 in the former section. 



Two large families in which this occurred may be quoted here, one 

 from a pair of Black without any admixture of Albino, and the other 

 from a Red pair carrying Albino. (Family I.E.) 



In the first instance, 1022 young were produced in three generations, 

 of which 70 had either both eyes or one eye No-white ; of the 47 Pure 

 No- white, 32 were unspotted and 15 spotted, that is about a third 

 spotted ; of the 23 one-sided No-whites, 11 were unspotted and 12 spotted, 

 that is a half spotted. 



In the other instance the proportions of spotted to unspotted were 

 quite different. 780 young were produced in one generation, 6 Pure No- 

 whites and 21 one-sided amongst them. Of the 6 Pure No-whites 

 2 were unspotted and 4 spotted ; whilst of the one-sided 2 were un- 

 spotted and 19 spotted. 



Taking all the records from all sources together and summing them 

 up shortly there were 32 spotted Pure No-whites ; of these 4 had large 

 spots or patches on the right side only, 10 on the left side only, 3 on 

 both sides, 2 dorsal, 8 on the 1st peraeon-segment, 4 both lateral and on 

 peraeon-segment, and 1 lateral, dorsal and on peraeon-segment. 



Whenever two unspotted No-ivhites of this kind have been mated 



