ZOOLOGY. 387 



in the monkey, the motor cortex of whose brain was destroyed. The 

 facts which have been obtained demonstrate that the so-called motor 

 cortex is not essential for the proper performance of movements. 

 We have also found that certain conditions facilitate the recovery. 

 These facts, and those obtained with paralyzed human patients, are 

 not only of considerable practical medical interest in that they show 

 that a paralysis due to a cerebral lesion is not an irrecoverable condi- 

 tion, but also that, contrary to the beliefs of both physiologists and 

 neurologists, the so-called motor cortex does not have the primacy 

 of function generally accorded it. They point to the necessity for a 

 new explanation or new explanations of certain cerebral functions. 

 For example, if a so-called ''voluntary" movement can be executed 

 after the removal or destruction of the parts of the brain (motor 

 cortex or underlying fibers) which have hitherto been considered to 

 be concerned with the production of such movements, we must alter 

 our conceptions of the functions of the so-called motor cells and 

 fibers. At the same time, if such an act of ''voUtion" can be carried 

 out without the parts of the brain which have hitherto been considered 

 to be primarily concerned in such ''volitional" acts we must modify 

 the current hypotheses concerning the relations of parts of the brain 

 to mental processes. 



ZOOLOGY. 



Castle, W. E., Harvard University, Cambridge, Massachusetts. Continua- 

 tion of experimental studies of heredity in small mammals. (For previous 

 reports see Year Books Nos. 3-14.) 



During the past year substantial progress has been made in the 

 study of inherited characteristics in guinea-pigs, rabbits, rats, and 

 mice, with special reference to the constancy and interrelations of 

 mendelizing characters. 



In the guinea-pig studies attention has been centered on size 

 inheritance in species crosses and on the influence of inbreeding on 

 size. In the rabbit work attention has been given principally to 

 quantitative studies of two color-patterns involving white-spotting, 

 the so-called Dutch and English varieties. Among the rats the selec- 

 tion experiments for modification of the hooded pattern, a mendeUzing 

 character, are being continued, now in their nineteenth generation, 

 and the linkage relations of two yellow varieties of recent origin are 

 being studied intensively. The mouse work centers upon a study 

 of the several allelomorphs of yellow, an unfixable because always 

 heterozygous character. 



Six minor publications dealing with this work have been issued 

 within the year and an extensive publication deahng with the work 

 on guinea-pigs and rats is now in press.^ 



^Sincc issue.! as Civrne^ie In-<t. W.ish. Pub. Xo. 2-11, 21 >< pp., 7 phtle^. 



