192 



SCIENCE 



[N. S. Vol. XXXI. No. 788 



still of the opinion that in normal years the 

 parasite would, in all probability, maintain a 

 general distribution (page 26). During the 

 spring and summer of 1909 a notable excep- 

 tion to this opinion existed in southwestern 

 Oklahoma. Here the green bug was abun- 

 dant over about one hundred square miles. 

 This area was examined, first by a representa- 

 tive from the federal bureau about the middle 

 of April and then by a member of the ento- 

 mological department of the university of 

 Kansas a month later, and neither of these 

 entomologists found any evidence of the pres- 

 ence of the parasite. Reliable reports subse- 

 quently made to the author showed the green 

 bugs present and the absence of the parasite 

 during the entire growing season and this in 

 a locality where parasites were superabun- 

 dant two years previous and in a climate 

 favorable to the existence and natural distri- 

 bution of the parasite. 



These are the evidences upon which the 

 opinion was based that this parasite does not 

 maintain a general distribution. 



5. What the reviewer says regarding the 

 Australian lady bird in California is impor- 

 tant. The only reference to this insect in the 

 bulletin is in connection with a historical 

 summary of entomological endeavor in the 

 control of one insect by the use of another. 

 Since this lady bird is not referred to in the 

 discussion of the green-bug problems, there 

 does not appear to be anything to show that 

 the behavior of this lady bird was used as 

 corroborative evidence to strengthen any con- 

 clusions regarding the green bug and its 

 parasite. S. J. Hunter 



Depaetment op Entomology, 

 Univeksitt of Kansas 



■ gametogenesis of the sawfly nematus 

 ribesn. a correction 

 In the Quarterly Journal of Microscopical 

 Science, Vol. 51, 1907, p. 101, I described ob- 

 servations on the gametogenesis of Nematus 

 rihesii, some of which subsequent work has 

 shown to be erroneous. Since my statements 

 have been quoted in several recent papers, I 

 think it necessary to correct the mistakes as 



far as possible, although I have not yet 

 reached a satisfactory solution of the phe- 

 nomena. The errors arose partly through 

 misinterpretation of the phenomena observed, 

 and partly through imperfect fixation, for I 

 find that, unless the material is very accu- 

 rately fixed, the chromosomes tend to adhere 

 together and give the appearance of a smaller 

 number than the true one. The same cause 

 has led other observers to make similar mis- 

 takes. 



Reinvestigation of Nematus shows, in the 

 first place, that there is only one division of 

 the spermatocytes; the first division described 

 in my paper is not a true mitosis, but is prob- 

 ably comparable with the abortive division 

 observed in the spermatogenesis of the bee. 

 I have not yet been able to determine the 

 chromosome number with certainty. In the 

 spermatogonia the number appears to be 

 about sixteen, and that in spermatocyte 

 mitoses about eight, but if eight is the true 

 reduced number, the occurrence of sixteen in 

 the spermatogonial mitoses of larvae derived 

 from parthenogenetic eggs is unexplained. 

 In the bee, and as I find, also in a cynipid (to 

 be published shortly), the spermatogonial 

 number is the same as that of the spermato- 

 cytes. 



I have not yet obtained fresh material for 

 reinvestigation of the maturation of the egg, 

 but the results of my recent work on the 

 spermatogenesis make it clear that my ob- 

 servations on the chromosomes in the polar 

 divisions also require revision. 



But the behavior of the chromosomes in 

 Nematus ribesii is so difficult to follow that it 

 is possible that the true interpretation will be 

 obtained only by the discovery of some nearly 

 related species in which they are more clearly 

 distinguishable. Leonard Doncaster 



UNIVERSITY OF Birmingham, England, 

 November, 1909 



mountain and valley winds in the canadiait 

 selkirks 

 To the Editor of Science : Report has been 

 brought from British Columbia by Mr. C. T. 

 Brodrick, of Harvard University, of an in- 

 teresting case of the daytime descent of air 



