FIN RAYS IN THREE SPECIES OF FUNDULUS. 



301 



The anal fin of the females of F. heteroclitus presents another 

 difficulty. On the anterior edge of this fin, and extending from 

 its base nearly half way to the tip, is a thick fold of skin enclosing 

 the oviduct (as stated by Jordan and Evermann '96). The 

 thickened skin extends backward over the bases of the first and 

 second rays, at least, and may make a count impossible without 

 dissection. 



The adult material for this study consisted of 40 males and 37 

 females of F. heteroclitus and 10 males and 22 females of F. 

 majalis, both species from a small salt water pond connected with 

 the head of Woods Hole Great Harbor, and also of 10 males and 

 1 6 females of F. diaphanus from Oyster Pond (fresh water) in 

 Falmouth, Massachusetts. 



Although the number of specimens is too small for statistical 

 accuracy, the results obtained show that the populations repre- 

 sented have considerably more variation in the number of fin-rays 

 than is indicated by the previously published descriptions of these 

 three species. 



Full descriptions have been published by Bean, '92 and '03, 

 Garman '95, Jordan and Evermann '96, Smith '07. In the 

 following table the results of the present investigation are given 

 in comparison with those of the authors just mentioned. 



Each one of the three species has on the average a characteristic 

 fin-pattern. In F. heteroclitus 12 is the most frequent number of 

 dorsal rays, but 1 1 and 13 are not infrequent. One specimen only 

 20 



