IOWA ACADEMY OF SCIENCES. 81 



NOTE ON THE TIME OF SEXUAL MATURITY IN 

 CERTAIN UNIOS. 



BY H. M. KELLY. 



Ill the coarse of a recent study* of the parasites of the 

 Unioniclse, 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 v^ith 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 unfor- 

 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 infertile 

 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-couq)l(uiatus,'f Alasuwdonta man/inafa, 



* H. M. Kel y,'99. Bull. III. State Lab. Nat. Hist., Vol V., .Art. VIII. "A Statistical 

 Study of the Parasites of the Unionidje. " 



t Those who are not acquainted with Simpson's recent classification of the UnionidK used 

 herein, will lind no difficulty in connecting these names with those previously in common use. 

 The specific names with proper inflectional endint.'s remain the same, except that Unio cor 

 nutus becomes Obliquaria reflexa. The genera Quadrula. Unio, Obliquaria, Plagiola and 

 Lampsilis are divisions of the former jrenus Unio, Alasmodonta is synonomous with former 

 Marginata, and Strophitus has been removed from Anodonta. 



