GENETIC TYPE AND THE ENDOCKINES 507 



Longitudinal sections of six pituitaries from F 2 hybrids 

 are shown in plates 95 (figs. 5 and 6) and 96 (figs. 1-4). 

 Some of the pituitaries from the F 2 hybrids present morpho- 

 logic patterns closely approaching those found in the two 

 parent stocks. Figures 5 and 6 (pi. 95) are of two such speci- 

 mens and should be compared with the bassethound and bulldog 

 glands (figs. 1 and 2). Figure 5 is from 1055 9 , shown from 

 life, together with three litter brothers, in plate 59 (p. 324). 

 The bitch was an almost perfect bassethound in type, while 

 a brother, 1053 $ , was the most completely bulldog typed 

 animal among the 150 F 2 bassethound-bulldog hybrids. In 

 the series of F 2 skulls in plate 57 (p. 321), his is first, at the 

 bulldog end (fig. 8) and hers is at the bassethound end 

 (fig. 15). The thyroid from 10555 is decidedly bassethound 

 in pattern (see fig. 1, pi. 94). The pituitary resembles very 

 closely that of the bassethound in figure 1, plate 95, and 

 shows no resemblance to that of the bulldog (fig. 2). This F 2 

 animal, 1055 9 , resembles the bassethound in general form, 

 thyroid pattern, and microscopic anatomy of the pituitary 

 gland. 



Figure 6 (pi. 95) approaches the bulldog pituitary type, 

 and is from a mature 16 months old F2 hybrid 1583 9 . The 

 proportions and arrangements in this gland closely follow 

 that of the bulldog (fig. 2). The pars intermedia is over 

 extensive and folds back on itself to give two layers of tissue 

 over the dorsal region of the pars nervosa. The pars distalis 

 is correspondingly limited in area, and its discoidal form 

 extends to the distal pole of the nervosa but fails to cover 

 its dorsal surface ; these are typical characters of the bulldog- 

 pituitary. No. 1583 9 had an extremely wide bulldog-like 

 head with deep depression at the nasion, and a short but 

 not fully bulldog muzzle. The thyroid gland of this bitch, 

 not illustrated, approached the bulldog type. The finer his- 

 tologic structure of the pars distalis shows a loose cord-like 

 arrangement of its cells with an excess of connective tissue 

 and small follicles with pale colloidal-like material at the 

 posterior region. This F 2 hybrid illustrates the definite as- 



