266 EXPERIMENT STATION RECORD. 



be looked at in the same way; but the extent to which the spot develops is a 

 more difficult, and perhaps, a different problem." 



Reversion in guinea pig's and its explanation, W. B. Castle (Carnegie 

 Inst. Washington Pub. 179, 1913, pp. 1-10).— The author summarizes the results 

 of his investigation as follows : 



" The agouti coat characteristic of wild cavies and of most other wild rodents 

 is dependent upon the presence in the fur of black pigment disposed in a definite 

 pattern with red (or yellow). The factors which control, respectively, the de- 

 velopment of black pigment and the production of the agouti pattern are inde- 

 pendent of each other. The agouti coat is obtained only when both these factors 

 are possessed by an individual. Only such agouti individuals as are homozygous 

 in both factors breed true under all circumstances." 



"An agouti animal which is homozygous in A (the agouti factor), but hetero- 

 zygous in B (black pigmentation), may produce agouti young and red ones, but 

 not black. An agouti animal which is homozygous in B, but heterozygous in A, 

 may produce agouti young and black ones, but not red. An agouti animal hetero- 

 zygous in both A and B may produce 3 sorts of young, agouti, red, and black. 

 All Fi (reversionary) agoutis produced by crossing black with red are of this 

 sort. Agoutis of the other 3 sorts are obtained only in the second or later 

 generations of agouti young." 



Reciprocal crosses between Reeves pheasant and the conimon ring-neck 

 pheasant producing unlike hybrids, J. C. Phillips (Amer. Nat., 47 (1913), 

 No. 563, pp. 701-704, fig. 1).—It is sho^sm that, unlike the case of many birds 

 (fowls, pigeons, canaries, and doves) which give evidence of sex-linked char- 

 acters, the pheasant hybrid shows "merely a different appearance of male 

 sexual plumage character in the Fi hybrids of a reciprocal cross between Reeves 

 pheasant and the common ring-neck pheasant." This phenomenon evidently 

 does not occur in the reciprocal crosses of other species of pheasants. No ex- 

 planation is offered for the present case. 



Some points of genetic interest in regeneration of the testis after experi- 

 mental orchectomy in birds, C. J. Bond (Jour. Genetics, 3 (1913), No. 2, pp. 

 131-139, pis. 2, figs. 5). — In investigations of the results of un44ateral oophorec- 

 tomy in rabbits, the writer observed that "the removal of one ovary in the 

 female rabbit is followed by a compensatory overgrowth in the remaining 

 ovary, and further that this hypertrophy affects both the Graafian follicles or 

 ova-bearing cells and the internal secretion-forming cells." It was found that 

 in birds " the same process occurs in the remaining testis after unilateral 

 orchectomy." 



It was further observed " in both male fowls and pigeons that when one or 

 both testes were removed intracapsularly— that is to say, when the testicular 

 substance had been apparently wholly removed and the capsule alone left, a 

 regeneration of the secreting tissue of the testis and the tubuli seminiferi took 

 place within the capsule so evacuated. . . . This regeneration must take place 

 either from the capsule, or more probably from microscopic fragments of 

 secreting tissue which are left adhering to the capsule at the time of the oper- 

 ation." The testis of the domestic fowl apparently has greater powers of 

 structural and functional regeneration after partial removal than exists in 

 mammals. 



With regard to "whether the gametes which are formed in this tissue re- 

 semble, in their hereditary characters, the gametes which are formed by the 

 original gland before removal," the author's investigation seems to indicate 

 " that the cell divisions of the motor sperm cells which provide the new sperma- 

 tozoa formed during regeneration of the testis do not take place in exactly 



