788 



SCIENCE 



[N. S. Vol. XXXI. No. 803 



many of the organisms present in manure 

 are not associated with the production of 

 malodorous compounds. 



Eeferenee is made (p. 145) to Bacterium 

 <icidi lactici in some cases and then again to 

 Bacterium lactis acidi, when evidently the 

 same organism is meant. This is apt to con- 

 fuse not only the beginner, but even the more 

 advanced student. 



Numerous typographical errors as mis- 

 spelled words, " dropped " lines, etc., occur, 

 but these are not so serious in a way, as they 

 can readily be recognized, but textual errors 

 as noted above are less easily perceived by the 

 student. 



Science should teach a student to be exact 

 and definite, but when texts are placed before 

 him that contain so many slips of the pen, it 

 sets a standard that makes for inferior work. 



H. L. EUSSELL 



/ SPECIAL ARTICLES 



NOTE ON THE CHROMOSOMES OF NEZARA. 

 A CORRECTION AND ADDITION 



In my preceding accounts of the chromo- 

 somes in Nezara hilaris (1905-06) I described 

 the idiochromosomes as being of equal size 

 and failed to recognize a dimorphism of the 

 spermatid-nuclei. I have recently discovered 

 that this was an error; and it is one that I 

 wish to correct in advance of a more detailed 

 description because Nezara now stands as the 

 original representative of that type of insects 

 in which neither a dimorphism of the sperma- 

 tozoa nor a quantitative difference of chrom- 

 atin between the sexes can be seen. 



That type was first based on the single case 

 of Nezara hilaris, but I afterwards added to it 

 the lygseid species Oncopeltus fasciatus on 

 the strength of Montgomery's earlier observa- 

 tions on the male and my own unpublished 

 ones on both sexes. I was led to reexamine 

 Nezara hilaris because of the discovery that in 

 the closely allied southern species N. viridula 

 there is a typical and very unequal pair of 

 idiochromosomes, which show the usual re- 

 lation to sex. The reexamination, in compari- 

 son with N. viridula, proves that in my earlier 



account the idiochromosome pair was incor- 

 rectly identified, and that in N. hilaris 

 there is in fact a slightly unequal pair of 

 idiochromosomes. This is, however, not the 

 smallest pair (which is common to the two 

 species) as both Montgomery and I were led 

 to believe from the size-relations seen in other 

 forms, but one of the largest; and in the 

 second division it does not lie in the outer 

 ring, as the small one does (a very exceptional 

 position for the idiochromosome pair, as I 

 pointed out) but occupies the typical position 

 at the center of the group. The inequality of 

 this pair in N. hilaris may readily be over- 

 looked, since it is but slightly marked — far 

 less than in N. viridula, and perhaps even a 

 little less than in Mineus, as heretofore 

 described. Moreover, both idiochromosomes 

 are more elongated than the other chromo- 

 somes and often of nearly the same diameter, 

 but differ in length. In polar views, therefore, 

 the inequality often can not be made out, 

 though in side views it constantly appears. 

 My former figure of such a view actually 

 shows an inequality of this pair, but insuffi- 

 ciently, the smaller member being represented 

 a little too long and thick. The inequality is 

 often more marked than in the particular 

 specimen there figured. 



Nezara can, therefore, no longer stand as a 

 representative of the " third type " recognized 

 in my paper of 1906, and Oncopeltus must 

 probably take its place. I say " probably " 

 because the case of Nezara shows how readily 

 a dimorphism of the spermatozoa may escape 

 detection when only a slight size-difference 

 between the idiochromosomes exists. Renewed 

 studies upon Oncopeltus (a very favorable 

 object) shows that a slight inequality of the 

 idiochromosomes may in fact often be seen at 

 every stage of the spermatogenesis, from the 

 pre-synaptic period onward. Quite as often, 

 however, they appear equal, and the size- 

 variation appears to lie within the range of 

 variability in the other chromosome-pairs. A 

 final decision in regard to this species is re- 

 served for a future more detailed account. 



A second point of interest, formerly over- 

 looked, is the existence in the second division 



