76 



Scientific Proceedings (97). 



question in his recent paper, it seems desirable, in advance of a 

 more extensive presentation, to describe briefly the various 

 anatomical findings which it can now be stated underlie the 

 albinous condition. 



The study of great numbers of such larvae produced by exper- 

 iment during the last three years, conducted, it is to be empha- 

 sized, both on living and on appropriately fixed specimens, has 

 given uniformly concurrent testimony that these hypophysis-free 

 albinos are produced by three chief alterations of the pigment 

 mechanism. These may be enumerated as, (1) Reduction in the 

 system of epidermal melanophores, consisting of greatly lessened 

 numbers of these cells and in the contracted and pigment-poor 

 condition of those cells which are present; (2) a marked reduction 

 in the number of so-called free pigment granules of melanin in the 

 epithelium; (3) an invariable expansion of the xantholeucophores 

 situated in both deep and superficial strata of the dorsum of both 

 head and body. 



The condition of the melanophores is especially interesting, 

 due to Atwell's contention that previous investigators have over- 

 looked what he feels to be the major contribution towards the 

 albinism made by a contraction of the subepidermal melanophores. 

 Atwell bases his contention on three lines of evidence: first, an 

 increase in the pigmentation, producing almost a normal depth 

 of color, when albinous larvae are treated with a solution of dried 

 pars intermedia substance; secondly, the preparation of many 

 whole mounts of the skin of albinous larvae in which he claims to 

 have discovered an invariable contraction of the deep melano- 

 phores; thirdly, observations on the living tail fin of albinous 

 larvae treated with an extract of pars intermedia where an expan- 

 sion of these cells was observed. It is only fair to state that full 

 admission is made of the reduction of the epidermal melanophores, 

 though this is rated as of secondary importance. Albinous larvae 

 have never in the hands of the writer been appreciably increased 

 in the depth of pigmentation even with the use of the one pro- 

 cedure most potent in expanding the subepidermal melanophores — 

 the sunlight. Moreover, it is extremely difficult to understand 

 Atwell's contention that the contraction of these cells is the main 

 cause of albinism when we are confronted with the anatomical 



