Februaby 1, 1907] 



SCIENCE 



191 



Fluid according to definition L. 



n 



astie 1 



Plastic solid L. 

 Fluid W. 



Solid L. and W. 



point 



CUi-p„ 



O 



Pressure. 



Figure illustrating varying conceptions, as to 

 where the line between fluid and solid should be 

 drawn. 



Neither definition is absolutely rigorous, 

 perhaps. It may be that every fluid can rest 

 under a very minute amount of strain, and 

 that every solid has plasticity. 



No discussion of fads can settle usage, so 

 I call for others, either here or in the scien- 

 tific meetings, to express themselves as to 

 what usage will best fit that of the past and 

 present, and be most practical for the future. 



Alfred C. Lane 



a correction 



To THE Editor of Science: To a communi- 

 cation by the writer, which appeared in Science 

 ior January 18, 1907, the name of the U. S. 

 Geological Survey was attached without au- 

 thority of the director. The writer wishes to 

 record his disavowal of any desire to commit 

 the survey to an indorsement of the senti- 

 ments expressed in said note. For these he 

 alone is responsible. In explanation he would 

 add that the note was written before the 

 writer became a member of the TJ. S. Geo- 

 logical Survey. It was not offered for pub- 

 lication, however, until about the time he was 

 planning to enter on field work, when his new 

 address was attached without due considera- 

 tion. 



Moreover, on deliberate reading, the writer 

 is conscious that unintentionally there ap- 

 pears to be in the language employed a tone 

 of discourtesy, which he regrets. 



C. H. Gordon 

 January 22, 1907 



SPECIAL ARTICLES 

 the case of anasa tristis 



In a paper read before the December meet- 

 ing of the American Society of Zoologists in 

 New York, illustrated by a very beautiful 

 series of photomicrographs taken from smear- 

 preparations. Miss Foot and Miss Strobell 

 announced the following conclusions, which 

 have since been published in a preliminary 

 form in the January number of the Biological 

 Bulletin: (1) There is no odd or 'accessory' 

 cln-omosome in Anasa tristis. (2) The num- 

 ber of spermatogonial chromosomes is 22. 

 (3) All the chromosomes divide in both ma- 

 turation divisions. The so-called odd or ac- 

 cessory chromosome is only a ' lagging ' chro- 

 mosome, and it divides with the others in the 

 second division. (4) The so-called ' chromo- 

 some-nucleolus ' of the growth period is not a 

 chromosome, but a nucleolus. 



These results are at variance with my own, 

 and since the differences in regard to the first 

 three involve the important more general issue 

 of the relation of the chromosomes to sex-pro- 

 duction, I will make the following reply. 



The fourth of the above conclusions, though 

 materially different from my own, is not alto- 

 gether irreconcilable with it. I have for some 

 time had reason to suspect (in case of certain 

 other genera) that a stage may have been 

 overlooked in the prophases in which the odd 

 chromosome temporarily loses its compact 

 nucleolus-like form. For the study of this 

 question smear-preparations offer decided ad- 

 vantages; and I am ready enough to admit 

 that in regard to these stages Miss Foot and 

 Miss Strobell may have made an important 

 addition to our knowledge, though I still be- 

 lieve that the ehromosome-nucleolus of the 

 earlier stages is the odd chromosome. On the 

 other and more vital points their results are 

 irreconcilable with my own, and only these 

 will further be considered here. 



Since the announcement of these results I 

 have carefully reexamined my old prepara- 

 tions (including those of Paulmier) and a 

 series of new ones from material collected 

 during the past summer. They include sec- 

 tions of material fixed in Flemming's, Her- 



