tripIve;t calves. 273 



rate with least loss of growth energy?" This point would 

 seem well worth investigation in the light of Hatai's valuable 

 hypothesis. It can, of course, be tested, as he has pointed out, 

 by finding whether a logarithmic curve will fit the observed 

 growth during the prenatal life of the twins. If so the hypothe- 

 sis will be satisfied. 



Still more interesting in the same connection is the case of 

 enzygotic twins, where the two individuals originate from the 

 same fertilized ovum. Such twins, so far as may be judged 

 from the meager evidence available, grow to the same end 

 adult size as individuals each developing from a single ovum 

 and occupying the uterus alone during gestation. But if this is 

 so it seems to raise a difficulty respecting the original endow- 

 ment of potential growth energy in the fertilized egg cell from 

 which the enzygotic twins arose. Did this fertilized egg have 

 twice the usual amount of potential growth energy? If not, 

 what is the source of the additional supply which makes each 

 of tlie enzygotic twins go on growing to normal full adult size? 

 It seems certain that the study of the growth, both prenatal and 

 postnatal, of multiple young in animals normally bearing but a 

 single offspring at a time, cannot fail to yield results of funda- 

 mental importance to the analysis of the normal physiology, of 

 growth. 



We may turn next to a description of the color characteris- 

 tics of the triplet calves. The three individuals were not all 

 'alike in color. The tAvo females were" very nearly alike but not 

 absolutely identical. The male calf was quite difl^erent in color 

 and color pattern from his two sisters. The general character- 

 istics of the triplets in respect to color pattern are shown in 

 figures 448 and 449. It is unfortunate that the photographs 

 from which these figures are reproduced were not better, but 

 they were the best it was possible to obtain. 



The male was a typical Guernsey in respect to coat color and 

 showed a very close approximation to the precise color pattern 

 exhibited by his mother. The color of that part of his coat 

 bearing pigmented hairs was a light yellowish fawn of the sort 

 frequently seen in Guernseys and exactly the same as that of his 

 mother. The similarity in color pattern between the male calf 

 and his mother is shown in Fig. 448. The mother had a white 

 triangle on the forehead like that of the bull calf; in the same 



