916 



SCIENCE 



[N. S. Vol. XLII. No. 1095 



limited pigment expansion was observed in the 

 light-adapted eyes of the lizard. 



With the exception of the early results of 

 Angelucci ('78), who maintained that definite 

 pigment movements occur in the rabbit, there 

 exists only one positive record for mammals — 

 that of Chiarini ('06), describing slight 

 changes in the retina of dogs which had been 

 exposed to direct sunlight and to darkness. 

 The pigment of the light-adapted animals ex- 

 tended in short fringe-like processes between 

 the rods, in contrast to the densely contracted 

 pigment of the reciprocal set. Finally, Garten 

 ('07)12 carried out carefully executed experi- 

 ments upon the ape, ox, rabbit and rat, yet 

 failed to observe any striking differences be- 

 tween the effects of light and darkness; how- 

 ever, in the retina of the ape, which has a mi- 

 nute amount of pigment, composed of needle- 

 like granules, the pigment was extended 3 to 

 4 granules deep in the light and only 2 to o 

 granules deep in the dark. 



When, in connection with experimentation 

 upon the retinal pigment and visual cells of 

 certain lower vertebrates, it became necessary 

 to review the literature of this subject, I was 

 at once impressed with the discrepancy between 

 the statements found in many standard texts 

 and the actual status of our knowledge, which, 

 I believe, has been correctly summarized in 

 the preceding paragraphs. 



That slight positional changes due to photic 

 stimulation have been detected in the retinal 

 pigment of certain mammals, is probably true, 

 but no evidence has yet been presented to show 

 that a like condition holds for man. More- 

 over, if, in the future, such responses are 

 demonstrated, the results upon other mammals 

 (ef. Garten's experimentation upon apes) 

 would lead us to expect them to be extremely 

 limited. Since it follows, therefore, that the 

 loose phraseology and the misstatements to be 

 found in many standard text-books necessarily 

 create fundamentally wrong impressions in 

 the mind of the reader, it is evident that the 



12 Garten, S., 1907, " Graef e-Saemisoh, Handb. 

 d. gesam. Augenheilkunde, " Bd. 3, Kap. 12, An- 

 hang. 



future editions of all offending texts should 

 avoid lending aid to the perpetuation of this 

 popular misconception. 



A phenomenon related to that of pigment 

 migration is the contractility exhibited by a 

 deiinite portion of the inner member of rods 

 and cones. The so-called " myoid " of the cone- 

 visual cell shortens to a marked degree when, 

 in the case of many fishes and of some amphib- 

 ians and birds, the retina is exposed to light. 

 Among reptiles and mammals, changes in the 

 length of the cone myoid are hard to observe, 

 yet in both groups responses to light have ap- 

 parently been detected in a few instances. 



Among mammals, the results of Stort ('87) 

 on the pig stand alone in ascribing striking 

 positional changes to the cones; Stort's meas- 

 urements of one dark-adapted human eye, 

 moreover, do not prove that movements of the 

 cones occur in man. Chiarini ('06) obtained 

 negative results on the dog's eye, although 

 Garten ('07), by careful experimentation upon 

 apes, has been able to demonstrate slight 

 changes in the region of the fovea. The as- 

 sumption, on the part of writers, of the occur- 

 rence of movements in the cones of man has 

 been relatively rare. 



The rod myoids of certain fishes, amphibians 

 and birds are likewise responsive when stimu- 

 lated by light, yet nothing has been recorded 

 concerning the existence of this phenomenon 

 in mammals. 



It is possible, as Garten ('07) suggests, that 

 the changes in the retinal pigment and visual 

 cells of mammals occur so quickly that the fix- 

 ing fluids through slowness of penetration fail 

 to preserve them in an extended condition. 

 Leslie B. Aeey 



TSE CONVOCATION WEEK MEETINGS OF 

 SCIENTIFIC SOCIETIES 



The American Association for the Advance- 

 ment of Science and the national scientific 

 societies named below wiU meet at Columbus, 

 Ohio, during convocation week, beginning on 

 Monday, December 27, 1915: 



American Association for the Advancement of 

 Science. — President Dr. "W. W. Campbell, Di- 

 rector Lick Observatory; retiring president. Dr. 



