136 THE JBIOLOGY OF TWINS 



place. But before entering upon a discussion of somatic 

 segregation, we must needs study some of the data upon 

 which the theory is based. Only a few selected cases may 

 be presented within the scope of the present volume ; the 

 reader is referred for complete data to two recent papers.^ 

 ■ For convenience of presentation it is necessary to 

 conventionalize the figures of band and scute doubling. 

 The methods of representing band doublings together 

 with the detail of actual cases are shown in Fig. 42. 

 At the top of the page is shown a single band with an 

 extensive doubling involving all but a few marginal 

 units at the right and the left. Directly underneath 

 is a conventional representation with numbers indicating 

 the numbers of scutes involved. Below this is another 

 type of doubling in detail, with the conventional repre- 

 sentation just beneath. Various types of scute doubling 

 are shown also, and the method of indicating the location 

 and distribution of them is by placing a small diagram 

 of a double scute in a band and locating its position 

 with reference to margin or middle by a number. In 

 doubtful cases an arrow points to the spot from which 

 the count proceeds. 



The character and distribution of inherited band 

 and scute doubling may be illustrated by a complete 

 detail drawing of the affected bands in one set of fetuses 

 (set K 87) and their mother (Fig. 42). The affected 

 band of the mother is marked M and those of the four 

 fetuses I, II, III, and IV. Fetuses I and II (a pair) 

 have each two affected bands. It will be seen that the 

 mother has a unilateral doubling involving 13-14 

 scutes six places from the left-hand margin, of band i. 



^ H. H. Newman, loc. cit. 



