786 



SCIENCE 



[N. S. Vol. XLIV. No. 1144 



Professor Shull 8 observed more carefully, 

 found that this was not the case, and concluded 

 that the synchronism observed by Dolbear was 

 an illusion. However, Shull observed certain 

 cases in which two individuals were in syn- 

 chronism. His observations are not open to 

 the objections raised in case of the fireflies, 

 because: first, there being only two crickets 

 concerned, the statistical fallacy does not 

 enter; secondly, his observations were repeated 

 and checked with great care, the rate of chirp- 

 ing being accurately timed. There can be no 

 doubt that Shull observed real synchronism 

 between two crickets at a time. But he says 

 (in a letter to me, dated October 8, 1916) : 



I am at present inclined to think that these 

 cases of synchronism were usually accidental. . . . 

 However, the insects do, I am sure, influence one 

 another. ... I regard it as still an open question 

 whether something more than chance was involved. 



In the article quoted, he questions whether 

 the synchronism may have been due merely to 

 temperature ; for at a given temperature nearly 

 all the crickets chirp at almost exactly the 

 same rate. 



In answer to our question whether animals 

 ever do maintain a synchronic rhythm of a 

 sort not included under (1) and (2) of my 

 fourth paragraph, we have found good evidence 

 for an affirmative answer only in the case of 

 crickets chirping. And in that case it is still 

 somewhat in doubt whether their simultaneity 

 is accidental, or due to the influence of envi- 

 ronment, or due to a lock and key adaptation 

 by which one cricket stimulates the other. If 

 any naturalist can give complete and accurate 

 observations on such synchronic rhythms, these 

 will be of great interest to the psychologist. 

 Wallace Craig 



University op Maine 



is cucumber mosaic carried by seed? 



In 1915 cucumber mosaic caused a rather 

 serious loss on one of the farms where cold 

 frame cucumbers are grown in the tidewater 

 section of Virginia. The same disease again 

 developed on this farm in the spring of 1916 



s Shull, A. F., The Stridulation of the Snowy 

 Tree-cricket (Q£canthu3 niveus), Canadian Ento- 

 mologist, 1907, Vol. 39, 213-225. 



on land which was in cucumbers last year and 

 also on land which had not grown this crop 

 for the past three years. This year as usual 

 the seed was sown in pots in the greenhouse 

 and the plants were transplanted to the cold 

 frames on April 5, 1916. 



On May 25, 1916, before the glass covering 

 had been removed from the cold frames, the 

 writer observed typical mosaic plants scattered 

 throughout the frames. A little later "white 

 pickle " fruits were also obtained from the 

 diseased vines. Of a total of 7,785 plants 110 

 were diseased on the above date. 



The cold frame growers in this section all 

 use one strain of forcing-cucumber seed which 

 they obtain from the same seed company. 

 On visiting the other cold frame farms during 

 the same week typical cases of mosaic were 

 found on three of the five farms and plants 

 suspected of the disease were observed on the 

 other two. Plants on one of the latter two 

 farms have since produced typical "white 

 pickle " fruits though the leaves are not stri- 

 kingly mottled. 



These observations indicated that the disease 

 was carried by the seed, but as in some cases 

 the diseased plants were growing on land which 

 had produced mosaic plants the previous sea- 

 son, there remained the possibility of a soil 

 factor. 



Data which made the matter of soil trans- 

 mission appear less likely was obtained from 

 cucumber plants which the writer was grow- 

 ing at the Virginia Truck Experiment Sta- 

 tion. These plants were from the same strain 

 of seed as that used by all of the cold frame 

 growers. The seed was planted April 27, 1916, 

 in a cold frame of steam sterilized soil which 

 had not previously grown a crop of cucumbers. 

 Of a total of 155 plants 58 typical mosaic 

 plants were observed on June 5, 1916. No in- 

 sects were observed on the plants up to that 

 time, probably due to the fact that the bed is 

 surrounded on three sides by a tall hedge and 

 on the fourth side by the station greenhouses. 

 The high percentage of diseased plants and the 

 failure to account for the disease in any other 

 way lead the writer to think that this mosaic 

 came from the seed. 



