IOWA ACADEMY OF SCIENCES. 
81 
NOTE ON THE TIME OF SEXUAL MATURITY IN 
CERTAIN UNIOS. 
BY H. M. KELLY. 
Iii the coarse of a recent study* of the parasites of the 
Unionidse, the following data in regard to the time of 
sexual maturity in certain species, and their method of 
carrying their glochidia, were obtained. This primary 
inquiry involved the microscopical examination of the 
sexual glands of each individual. And in females whose 
gills were found swollen with the sexual product, the por- 
tion of these organs forming the marsupium and the stage 
of development of its contents, were also noted. 
The examinations were made at three seasonal periods: 
(1) in the latter part of April and through the month of 
May; (2) through July and the first half of August; (3) 
through October and in early November. It is unf or- 
nate that the two gaps thus made — the month of June, 
and the latter part of August and all of September — occur 
well within the limits of the times of sexual activity. 
This, with the comparative scantiness of material in cer- 
tain species, at the critical period, has reduced the value 
of the observations. Where, however, blanks occur in the 
following tabulation, it is often not difficult to infer the 
condition from either the state of the other sex at that 
time, or from the result of later examinations of the same 
sex. 
With the exceptions noted below, the Unios examined 
are from the vicinity of Havana, Illinois, and Mount Ver- 
non, Iowa, and of species common to the two regions. 
Data from Unio-complanatus , f Alasmodonta marginata , 
* H. M. Kel y, ’99. Bull. 111. State Lab. Nat. Hist., Vol V., Art. VIII. “ A Statistical 
Study of the Parasites of the Unionidae. ” 
fThose who are not acquainted with Simpson’s recent classification of the Unionidae used 
herein, will find no difficulty in connecting these names vtith those previously in common use. 
The specific names with proper inflectional endings remain the same, except that Unio cor. 
nutus becomes Obliquaria reflexa. The genera Quadrula, Unio, Obliquaria, Plagiola and 
Lampsilis are divisions of the former genus Unio, Alasmodonta is synonomous with former 
Marginata, and Strophitus has been removed from Anodonta. 
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