October 21, 1920] 



NATURE 



25' 



object of the author is to show that in the presence 

 of greater numbers of models the mimics are found 

 to be true to type, but that when they outnumber the 

 models many transitional and other varieties are pre- 

 served. The paper is a confirmation and extension of 

 the author's earlier article published in March, 1914. 

 The destruction of butterflies, so far as selective action 

 is concerned, is held to be mainly the work of young 

 birds which have to learn what to eat and what to 

 avoid. Thus in 1914, when the models were extremely 

 abundant, any member of a combination would have 

 been more likely to be the distasteful Acraeine. The 

 young birds would therefore leave that combination 

 alone, while varieties of the Pseudacraea not con- 

 forming' to the model would be destroyed. As the 

 birds grew older, and in localities where the models 

 had become scarcer, one must suppose that the birds 

 had forgotten what the latter tasted like, so that no 

 one form of Pseudacriea had much more chance of 

 surviving than any other. This explanation pre- 

 supposes that the bird fauna stays on an individual 

 island and does not fly from one to another. Dr. 

 Carpenter has already brought forward some 

 evidence which suggests that this is actually what 

 does occur. 



.Messrs. .\. S. Kennard and B. B. Woodward have 

 published in the Proceedings of the Malacological 

 Society for September some " Nomenclatorial Notes 

 relating to British Non-marine Mollusca." .After dis- 

 cussing the names of various species of Testacella and 

 Helix, they point out that the genotype of .'\ncylus is 

 Patella lacustris, Linn., and that Ancylus fluviaiilis, 

 which belongs to a different genus, must be called 

 Ancylastrum. This is a most unfortunate conclusion, 

 because it is the latter species that has given the name 

 to the well-known .'\ncylus Lake and Ancylus Clay of 

 the late Glacial period in North-West Europe. Scarcely 

 less regrettable is the authors' desire "to once again 

 point out " that the name Bulinus is not available for 

 " the Egyptian shells [sic] which play the part of host 

 to Bilharzia," or, indeed, for any mollusc. They may 

 be right, but we do not agree that because O. F. 

 Miiller adopted Adanson's pre-Linnean name Bulinus 

 for four species, one of which was that imperfectly 

 described by Adanson, his action "of course involves 

 the acceptance of [Adanson's] shell as the type of the 

 genus." The authors are so severe on Dr. .Annan- 

 dale for thinking that the name Bulinus (or Bullinus) 

 ought to be preserved because of its wide currency, 

 that one is astonished to nnd them, almost with the 

 same pcnful, writing of Bilharzia, which they must 

 know to be a synonym of Schistosoma. It is doubt- 

 less their misfortune rather than their fault that pages 

 which blame the eccentric Fitzinger for neglect in 

 proof-reading should themselves exemplify that form 

 of carelessness. 



From Buenos Aires wt .,.i.> i.v.,ii.) u. t,»,:,l .1 

 copy of £1 Hornero, a journal of Argentine ornitho- 

 logv published by a recently established society. La 

 Sociodad ornitol6gicn del Plata, constituted for the 

 onrouragcmcnt of the study of the birds of the 

 southern portion of South America. The journal 

 <!crives its name Hornern from the Spanish word 

 NO. 2660, VOL. 106] 



denoting one of the most characteristic birds of 

 Argentina, known to Englishmen as the oven-bird 

 and to science as Furnarius rufus, and an illustration 

 of the birds and their curious massive nest built up of 

 clay adorns the cover of each issue. The present 

 number contains a carefully prepared list of the dif- 

 ferent species of penguins found along the coasts of 

 Argentina drawn up by Senor R. Dabbene, the editor 

 of the journal, and a list of 254 species of birds found 

 in the neighbouring Republic of Uruguay from the 

 pen of Senor J. Tremoleras, of Montevideo. Mr. 

 A. G. Bennett, of Port Stanley, in the Falkland 

 Islands, contributes some notes on the habits and dis- 

 tribution of the marine birds of that distant outpost of 

 the British Empire, illustrated by reproductions of 

 photographs taken by himself. The parasitic Mallo- 

 phaga of the .Argentine are treated of at considerable 

 length by Dr. F. I^hille, who has himself described 

 31 out of the 159 species known to exist in the 

 Argentine ; and, finally, Prof. Lucas Kraglievich has 

 an article on the fossil birds of the Republic, in which 

 he discusses the relationship of Phororhacus with the 

 recently described Diatryma of the Eocene beds of the 

 United States. There are a number of shorter articles 

 and notes, with an ample bibliography of recent pub- 

 lications dealing with South American ornithology, 

 and the general get-up and editing of the journal 

 reflect great credit on the Sociedad ornitol6gica del 

 Plata and the editor, Seftor Dabbene. 



Mr. W. H. Taliaferro records {Journ. Exper. 

 Zool., vol. xxxi.. No. I, July, 1920) the results of 

 observations on the reactions to light in Planaria 

 maculata, planned with the object of ascertaining 

 how far, in this Turbellarian, the function of the 

 eyes in the reactions to light can be correlated with 

 the histology of these organs. Hesse (1897), who 

 worked with certain Triclads which were negative to 

 light, and hence moved away from the source of 

 stimulation, maintained that this reaction was due 

 to the fact that the sensory cells or rhabdomes were 

 shaded by the pigment-cup which partially enclosed 

 them, whereas when the worm turned in any other 

 direction the pigment-cup did not shade all the 

 rhabdomes. When certain of the rhabdomes were 

 illuminated, as in the latter case, the animal turned 

 so as to bring the sensory region of the eye again 

 into the shadow of the pigment-cup. Hesse therefore 

 maintained that the localisation of the photic stimulus 

 is the specific function of the pigment-cup, which 

 enables the animal to direct its course away from 

 the source of light. .Mr. Taliaferro has carried out 

 experiments on normal Planaria and on others from 

 which one of the eyes, or a portion thereof, has been 

 very carefully removed. He shows that the rhab- 

 domes in the eye are arranged in two localised sensory 

 regions. Illumination of one set is followed by the 

 animal's turning towards the side containing the 

 eye, while illumination of the remaining rhabdomes 

 is followed by the animal's turning in the opposite 

 direction. The observed reactions can be explained 

 without assuming (with Hosse) that the pigment-cup 

 acts as a localiser of photic stimuli. Light must 

 strike a given rhabdome parallel to the long axis of 



