SO CHARLES V. MOKKIII 



ing the chromosome groups in the oogenesis, fertilization and 

 cleavage in certain coreid hemiptera and of determining in this 

 way, if possible, whether the assumptions' made in regard to tin- 

 number and behavior of the chromosomes in these stages is in 

 accordance with the facts. 



Four species of the Coreidae were examined: Archinierus altcr- 

 tiatus Say, Anasa tristis De Geer, Protenor beljragei Hagl., Chelini- 

 dea vittigera Uhler. 2 In all of these forms the spermatogonia 

 have been found to contain an odd number of chromosomes, one 

 of which (the unpaired idiochromosome 3 ) fails to divide in one of 

 the maturation divisions. One half the spermatozoa thus con- 

 tain this chromosome, the other half lack it, and a dimorphism of 

 the spermatozoa arises. The oogonia have been shown to have 

 an even number of chromosomes, the unpaired element of the 

 spermatogonia being represented here by a pair of equal size. 

 The maturation of the egg had not been fully worked out, but 

 it was assumed that every chromosome divides equally in both 

 polar divisions, giving to the mature egg a group of chromosomes 

 similar to that borne by a spermatozoon having the idiochromo- 

 some. The eggs were accordingly assumed to be all of one kind 

 with respect to their chromatin content, as direct observation 

 has shown to be true in phylloxerans (Morgan), aphids (Stevens, 

 von Baehr) and more recently in Heterakis (Boveri and Gulick.) 



atory. Woods Hole, Mass., in 1909. To the directors of these laboratories I am 

 indebted for the facilities placed at my disposal. I wish also to express my grati- 

 tude to Professors E. B. Wilson and T. H. Morgan for the many helpful suggestions 

 they have made during the progress of this work. 



: I am indebted to Mr. E. P. Van Duzee, of Buffalo, N. Y., for the identification 

 of my material. The species Archimerus altcrnatns is almost, if not quite, identical 

 with the A. calcarator of Professor Wilson's material (identified by Mr. P. R. Uhler) 

 and was collected from the same locality in Van Cortlandt Park, NV\\ York. Pro- 

 tenor was found at Woods Hole, Mass., and Anasa at Woods Hole, and Cold spring. 

 Harbor, N. Y. Chelinidea was taken by Professor Wilson at Southern Pines, N. C. 

 A part of the living specimens of Anasa were also furnished by Professor \Yilson 



3 For the sake of simplicity, the term "idiochromosomes" will be used in this 

 paper to designate those chromosomes which are associated \\itli sex-production, 

 irrespective of their detailed behavior in the growth periods or maturation division*. 

 It will thus include the "idiochromosomes" (in the more restricted sen-n, "acces- 

 sory," "odd" or "hcterotropic" chromosomes, "monosomes," "heterochromosomes," 

 "X- and Y-clements," etc., of recent writers. Professor Wilson ha- u^-.l this term 

 in a similar sense in the fourth of his "Studies" ('ogb). 



