510 CHARLES ZELENY AND C. T. SENAY 



quency distribution gives a major mode at 27.4 jj. and a minor 

 one at 28.8 fx. The minor mode may be accidental though such 

 an irregularity is not common in frequency distributions in a 

 population known to be homogeneous. 



There are no data available concerning the spermatogenesis 

 of this species but Montgomery ('06) has described two kinds 

 of spermatids for other members of the family. 



4. Euschistus variolarius, a hemipteran. Material was ob- 

 tained during April. All the spermatozoa were not fully devel- 

 oped and selection was necessary to insure the exclusion of the 

 unripe ones. Five hundred measurements were made. The re- 

 sulting curve as shown in figure 5 is distinctly bimodal with 

 modes at 15.1 n and 16.5 m and with an inequality favoring the 

 larger spermatozoa. The ratio between the modes is 1.00 : 1.09. 



E. B. Wilson ('06) described an ''X" and a "Y" chromosome 

 for this species. The expected ratio as approximated from his 

 figures of the chromosomes is 1.00 : 1.04. This does not agree 

 at all well with the ratio between the modes as given above. 

 This result is contrary to that obtained for several species by 

 Zelenj^ and Faust ('15) which showed a striking similarity be- 

 tween the two calculations. 



5. Cosmopepla carnifex, a hemipteran. The material was ob- 

 tained in May and the spermatozoa were all active. Five hun- 

 dred measurements were made. The resulting curve as given 

 in figure 6 shows well marked bimodality with approximate 

 equality in the two groups. The modes are at 18.5 m and 19.9 n 

 and give a ratio of 1.00 : 1.075. There can be no doubt in this 

 case of the existence of two fairly equal size groups. 



Montgomery ('06) describes two kinds of spermatids for this 

 species, pne with seven chromosomes plus an "X" and the other 

 with seven plus a "Y." The figures are not suitable for the 

 determination of the chromatin ratio. The ratio in another 

 Pentatomid, Euschistus variolarius, is 1.00 : 1.04. 



6. Passalus cornutus, a coleopteran. Material was obtained 

 at the end of March and the spermatozoa were uniformly ripe 

 and active. Five hundred spermatozoa were measured. Neglect- 

 ing the minor projection at the right, the curve as given in figure 



