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SCIENCE 



[N. S. Vol. XL. No. 1025 



BrirLkmann.2 Weber maintains tHat the black 

 pigment granules of those organs are partly 

 distributed like fine dust particles in the cells, 

 partly united in small lumps, and the pigment 

 is mixed with the secretion. He observed 

 chromatophores which entwine the grandular 

 acini, but emphasizes that the pigment is not 

 derived from these acini, but from the sebace- 

 ous cells themselves. Beccari and Brinkmann, 

 on the other hand, have more recently and 

 independently of each other made the obser- 

 vation that the pigment is not formed in the 

 glands themselves, but in the chromatophores 

 mentioned by Weber and transported as 

 finished products into the glands. Brinkmann 

 describes the process as follows: 



The chromatophores, or more correctly the 

 melanoblasts, as I call them, originate in the con- 

 nective tissue, they are strongly anastomosing 

 structures which, laden with melanin, migrate as far 

 as the alveoli of the sebaceous glands. They are 

 not only entwined by them, as Weber thinks, but 

 the melanoblasts penetrate the connective tissue 

 capsule of the gland and push themselves in be- 

 tween the cells of the gland. According to Bec- 

 cari 's investigations the amceboid process of the 

 melanoblasts penetrate into the cells and deposit 

 their pigment: this last phenomenon I could not 

 confirm by direct observation, only the fact that 

 they migrate into the cells. 



Another noteworthy view that may be cited 

 from the vast literature on the subject is that 

 of Jarisch, who holds that there is a definite 

 relation between the nuclear chromatin and 

 pigment; certain: chromatin particles, the 

 tingible or pyrogenous bodies, are formed and 

 changed into pigment balls. Luckjanow and 

 Steinhaus have actually observed pigment 

 masses arising around the nucleus in sarcoma 

 and Maurer and Fraisse confirm this observa- 

 tion for the epithelial nucleus of Pleurodeles 

 when it is the result of the degeneration of the 

 nucleus being accompanied by the shrinking 

 of the nucleus. This reminds us very vividly 



2 N. Beccari, ' ' Eicherche rntomo alle tasche ed 

 ai corpi ghiandolari suborbitali in varie specie di 

 Euminanti," Arch. ital. di Anatom e di Embriol., 

 "Vol. 9, 1910. A. Brinkmann, "Bidrag til Kimis- 

 haben om Drijvtyggernes Hudkirtelorganer Vi- 

 densk. Medd. fra nath. Foren, " Kobenhavn, 1911. 



of Richard Hertwig's doctrine of the chro- 

 midial apparatus which involves the migration 

 of chromatin particles from the nucleus into 

 the cytoplasm. Goldschmidt very ingeniously 

 enlarged this doctrine into the doctrine of the 

 duality of the nucleus, according to which 

 every animal cell is doubly nucleated, con- 

 taining a somatic and a reproductive or genetic 

 nucleus, the former performing the functions 

 of metabolism and motion, the latter that of 

 reproduction and transmission, the somatic 

 nucleus representing Hertwig's chromidial 

 apparatus. I mention all these recent views 

 on the possible origin and nature of pig- 

 ment formations, because they throw some 

 light on my own observations. The histo- 

 logical knowledge of the mantle tissues of the 

 oyster is still very inadequate, notwithstanding 

 the classic investigations of Eawitz on "Der 

 Mantelrand der Acephalen." We know in a 

 general way that the epidermis consists 

 largely of cylindrical cells, many of which are 

 goblet cells filled with mucus; others are 

 ciliated pigmented and nonpigmented cells, 

 especially along the mantle edge. There are 

 also numerous small mucous glands active in 

 the formation and growth of the shell; a rich 

 nerve plexus enervates the mantle edge and a 

 large blood vessel with numerous blood 

 lacunae supplies the necessary food while a 

 series of muscle bundles controls the contrac- 

 tion and expansion of the mantle. I made 

 careful histological sections of the mantle of 

 oysters not exposed to the direct rays of the 

 sun, as well as of those that had been exposed 

 various lengths of time. I also macerated 

 blackened mantle tissue in the fresh state. 

 In the unexposed specimens the pigment was 

 confined to cylindrical cells along the mantle 

 edge. The pigment granules were evenly dis- 

 tributed throughout the cytoplasm in most 

 cases; in some there was a denser massing of 

 granules along the outer margin of the cells, 

 otherwise the mantle was free from pigment. 

 Sections of the exposed mantle showed the 

 presence of pigment granules in all the cells 

 of the epidermis not only in the mantle but 

 also in the gills and in the connective tissue 

 cells of the pericardium. Macerated mantle 



