No. 642] SHORTER ARTICLES AND DISCUSSION 



189 



generation (viz., A, B, and C) are as follows: 



Z, = 0, Z, =25, 



Z2 = 25, Z, =34.37, 



Z3 = 25, Zt, = 27.1, 



i.e., in five generations of ancestry the inbreeding is about a 

 quarter of the possible maximum. 



There is no deleterious effect of inbreeding apparent iA this 

 pedigree. The three children in the last generation, the most 

 inbred of any, show no signs of abnormality. In their father's 

 fraternity, for which Z, =Z, = Z3 = 0; Z, = ]2.5; Zt4=4.1, 

 or in four generations of ancestry there is i/^.-, of the possible 

 maximum inbreeding, one of eight died of tuberculosis: the 

 other seven have attained adult age. In the mother s fraternity, 

 for which Zi = Z, = Z, = 0: Z, = 6.25: Zt, = 2.0. two out of 

 the three have died of tuberculosis. Tlir least iiilu-ed. there- 

 fore, show the greatest susceptibility to tuhfrculo>is. Tlie num- 

 bers are, of course, too small to draw any ccrtaiu iufererici'. ])uT. 

 so far as they go, they accord best with thr view that there 

 is no harmful effect of inbreeding per se. 



ON COLOR VARIATIONS IN CIIITOX.S 

 "The question was raised by Bateson ("Materials," 18f)4, 



a sorirs. Witli this point in mind he examined a eolleetion of 

 chitons, the sh,,-ll plates of these animals providing an excellent 

 opj)ortiinity for such observations. He found color variatious 

 affecting all the plates of an individual to l>e of rather rare occur- 

 rence, but that plates 2, 4 and 7 seemed, on the otlier hand, to 

 exhibit a decided tendency to vary togeth(T (in several species of 

 Chiton). 



Although the problem of metanuTisin, so tar as it coiH^rns 

 variation, has perhaps lost some of iK ori-inal attrartivmrvs. I 



