OCR Text |
Show 1903.] IN FANCY MICE AND RATS. 77 that colour may be influenced by structure, and structure by colour, must be remembered. Naturally we may inquire whether albinism in M a n is not a similar recessive. Castle has given evidence pointing in this direction. The occurrence of albinism in the families of first cousins (see Day, Seligmann, &c.) is consistent with this view; but there are a few recorded cases of the occurrence of albinos in the offspring of albinos breeding with normal parents, where the hypothesis that the normal parent was D R is not at all easily admissible. No case of the union of two human albinos is known to me. The matter cannot here be further discussed, and the reader must refer to the literature, the most important paper being that of Cornaz*. There are a few cases on record where the production of albino offspring by animals and plants must almost certainly be regarded as the occurrence of a new and original variation, though the cause of such sporting is entirely unknown. W e here encounter the first problem calling for experimental study. What is an albino ? W e know that it appears to form no pigment; but such a body has other characteristics also. While the blood of pigmented animals shows intravascular clotting on the injection of nucleo-proteids, that of the albino is declared to be unaffected. The mountain hare is said in this respect to behave as a normal in its summer coat, but as an albino after the winter change. How these differences are related to the want of pigment we do not know. Such an inquiry offers a wide field for experiment. In particular, we ought to know how the albino or the normal behaves towards the nucleo-proteids of an albino, and so forth. However this may be, there seems to be but little doubt that the albino-bearing gametes can generally segregate that character entire, as they divide from the colour-bearing gametes of the hybrid zygote of any colour; and if we knew more clearly what is the real physiological difference between colour-secreting and albino organisms, w e might get a clearer conception of the nature of such segregation. W e may consider next the work of Crampe, which is on a large scale and relates entirely to Rats. His latest paper is dated 1885 (10), and consequently is pre-Mendelian in treatment. He bred nearly 14,000 rats, and made elaborate records and tables of conclusions. Many of these observations are readily available so far as they provide simply qualitative as opposed to quantitative evidence ; but after many attempts I have not succeeded in unravelling the material enough to group the statistics in Mendelian form f. Though only a sketch can be here given, many of * The student of albinism who refers to the paper of Legrain (Bull. Ac. Med. Bruxelles, ix. 1866) should remember that it is the curious instance cited by Darwin (Life and Letters, i. p. 106) as a deliberate invention. + The figures given (10) pp. 555 & 612 are the likeliest, but even these obviously contain certain heterogeneous elements now not distinguishable with confidence. |