February 9, 1922] 



NATURE 



187 



Research Items. 



Culture of Ancient Peru. — One difficulty in 

 the sequence-dating of the textiles of ancient 

 Peru, which, with the pottery, are the best evi- 

 dence of the pre-Spanish culture, is that Peruvian 

 looms are very scarce in museums, and, when found, 

 are usually incomplete, and almost invariably undat- 

 able, even in accordance with the sequence-dating at 

 present accepted. In Man for December last, Mr, T. A. 

 joice reports that a vase presented to the British 

 Museum in 1913 by Sir Herbert Gibson shows a de- 

 finite and indisputable correlation between a certain 

 type of loom and a certain type of pottery. This 

 vase, which definitely belongs to the Proto-Chimu 

 period, that is to say, the earliest period of anv sort 

 of developed culture on the northern Peruvian coast, 

 presents a scene showing the weaving of tapestry on 

 a loom without a treadle, and associated with pottery 

 also belonging to the same early period. It does not 

 prove, but it suggests, that the principle of the treadle 

 was unknown to the Proto-Chimu weaver; if so, 

 then the treadle belongs to a comparatively late period 

 of South American culture. Much further inquiry is 

 needed before the significance of this discovery can 

 be used as a proof of sequence-dating. 



Parasitic Worms from Animals. — Dr. G. A. 

 MacCallum gives (Zoopathologica, vol. i. No. 6, 

 1921, published by the New York Zoological 

 Societ\) an account of parasitic worms from animals 

 in the New York Zoological Park and Aquarium, 

 with a figure and brief description of each species ; 

 some of the descriptions, however, are too brief and not 

 altogether serviceable. A new species of Heronimus 

 is viviparous — the uterus contains miracidia. The 

 author, who is pathologist to the New York 

 Zoological Society, deserves commendation for his 

 zeal in searching for and recording the parasites of 

 the animals which pass through his hands. 



Indian Marine Polych^ta.— A further instal- 

 ment of the reports on the fauna of the Chilka 

 Lake has been published in vol. 5, No. 8, of 

 the Memoirs of the Indian Museum. This part 

 contains a systematic account of the Polj-chaeta by 

 Mr. R. Southern, who also reports on collections 

 from the Gangetic delta and from the Cochin back- 

 water. The majority of the species live either in 

 brackish water of low salinitv or are euryhaline, i.e. 

 can live in water the salinity of which varies between 

 wide limits. Euryhaline forms appear to be relatively 

 more numerous in India than in Europe, and Mr. 

 Southern suggests this adaptation mav be correlated 

 with the sharp division of the climate into wet and 

 dry seasons, one result of which is that the littoral 

 region, especially in bays and estuaries, is periodically 

 flooded with water of low salinity. Mr. Southern 

 points out that there are so few "records of Indian 

 littoral marine Polychaeta that there is no basis for 

 instituting a comparison between the Polychaeta of the 

 lake and those of the seashore. Of the twenty species 

 from the lake, eighteen are described as new. The 

 collection has a typicallv marine facies, and probably 

 represents an impoverished remnant of the Polvchaeta 

 which inhabited the open bav before the present lake 

 was almost completolv cut off from the Bay of Bengal 

 by the spit of sand which forms its eastern boundarv. 



Selection Experiments with Ci.adocera.— Dr. 

 A. M. Banta has published CCarnfcie Institution of 

 ^^^^shtngton, Publication No. 305) the results of 

 NO. 272S, VOL. 109] 



extensive selection experiments with Cladocera. 

 He chose responsiveness to light, as measured by 

 reaction-time, and selected simultaneously in different 

 strains for increase and decrease of this physiological 

 character. Pure lines of Simocephalus and Daphnia 

 have been bred parthenogenetically for more than 

 eight years. In such parlhenogenetic eggs there is 

 only one maturation division, and in the absence of 

 a reduction division there is apparently no oppor- 

 tunity for segregation or recombination of genetic 

 materials. In the course of the experiments a great 

 deal has been learned about the biology of^ the 

 organisms, and their reactions to varying environ- 

 ments. Selection experiments produced a significant 

 difference between plus and minus strains in only 

 one of fifteen distinct lines studied, although there 

 were indications of an effect in several others. The 

 nature of this effect of selection is discussed at length. 

 The change appears to have been a gradual one, 

 which can scarcely be accounted for by the occurrence 

 of a few marked mutations. The two strains ob- 

 tained differed only in reactiveness to light, and this 

 difference was maintained for at least 112 generations 

 after selection ceased. These results would appear 

 to limit the universal application of Johannsen's law 

 that selection within the pure line is of no avail in 

 modifying its genetic properties. 



Factors of Growth and Multiplication. — 

 Two recent papers (Biochemical Journal, vol. 15, 

 pp, 595-612) by Prof. Brailsford Robertson contain 

 some important observations on the mutual influence 

 of individual organisms in promoting growth and 

 multiplication. Working with the ciliated protozoon 

 Enchelys, he shows that it feeds mainly upon bacteria, 

 and that its rate of growth is much influenced by 

 some soluble thermostable substance which arises 

 from them. During the early stages of development 

 of a culture the multiplication rate increases progres- 

 sively with each division, and partakes of the auto- 

 catalytic character which has been previously described 

 in various animals and plants from man downwards. 

 This has nothing immediately to do with its food, but 

 depends on the contiguity of the infusoria, and in a 

 special series of experiments Prof. Robertson shows 

 that a culture started with two individuals will pro- 

 duce, not twice, but about five times as many 

 descendants in twenty-four hours as a culture started 

 with a single Enchelys. Conjugation was never seen 

 under the conditions of the experiments, and the effect 

 appears to be due to soine accelerator substance 

 produced by the protozoa in the presence of the 

 accelerator arising from the bacteria. It would be of 

 much interest to determine whether the same pheno- 

 mena accompany the growth of an organism feeding 

 only on soluble substances such as the bacteria-free 

 race of the ciliate Colpidium described by Dr. Peters 

 (Journal of Physiology, vol. 55, p. i), where the condi- 

 tions are much simpler than those examined by Prof. 

 Robertson. 



Mixed Products of Granitic Intrusion. — Mr. 

 Charles H. Clapp, in his study of "The Geology 

 of the Igneous Rocks of Essex County, Massa- 

 chusetts " (U.S. Geol. Survey, Bull. 704, 192O 

 makes a noteworthy claim for regarding several un- 

 usual types of rock as products of the intermingling of 

 an invading granite with material derived from the 

 cover into which it penetrates. He recognises a gravi. 



