GENETIC TYPE AND THE ENDOCRIXES 471 



determinant, which is certainly not true in this case. Like- 

 wise, the hackcross on the dachshund presents even chances 

 for pituitary patterns of the F x hybrid or dachshund type. 



Figures 1 and 2 in plate 90 illustrate longitudinal sections 

 through the pituitaries from backcross Boston terriers, and 

 figures 3 and 4 show similar sections from the backcross on 

 the dachshund. The resemblance of these sections to those 

 from the two parent stocks and to those of the Fj hybrids 

 may be estimated by a comparison with the photomicrographs 

 in plates 87 and 88. 



Figures 1 and 2 are from 524 6 and 525 9 , brother and 

 sister litter mates. Their dam was Boston terrier 435 9 and 

 the sire was 128 5 Fj hybrid. The brother and sister are 

 shown from life in plate 44 (fig. 1) (p. 247). They are both 

 brindle in color, with long legs and somewhat shortened, 

 bent tail, indications of the Boston terrier stock. Their skull 

 measurements fall between those of the F, hybrid and the 

 Boston terrier parent, and they are not so strongly Boston 

 terrier-headed as some backcross hybrids, as, for example, 

 635 6 (right in fig. 2, pi. 44). 



Figure 1 in plate 90, from backcross Boston terrier 524 6, 

 gives a picture that is strikingly similar to figure 5 in plate 

 88, a pituitary from an uncle, 129 i Fj. The enormous cysts 

 and the nature of their epithelial lining as shown in the pars 

 tuberalis and anterior region of the pars distalis, as well 

 as the cellular composition of the differentiated portion of 

 the pars distalis, are closely similar in these two sections. 

 The pars intermedia and nervosa in the backcross pituitary 

 suggest the Boston terrier somewhat more closely than they 

 do the corresponding parts of the F x gland. The reader 

 will realize, however, that these comparisons of histologic 

 deviations from the normal cannot be emphatically stated, 

 since wide variations exist and the physiologic and type 

 significance of such conditions are at present only partly 

 understood. The point of real importance in the present 



