CONTACT ORGANS IN THE KILLIFISHES OF 



WOODS HOLE. 1 



H. H. NEWMAN. 



In a former paper 2 the writer had occasion to describe certain 

 .interesting structures occurring as a secondary sexual character 

 in the spawning males of four species of Pceciliidae occurring in 

 the waters about Woods Hole, Mass. These structures were 

 designated "contact organs," the writer venturing to use a new 

 term for the reason that no very similar structure had been pre- 

 viously described. Contact organs seem to have a somewhat 

 similar function to that of the pearl organs of other authors, but 

 in structure they are utterly different. 



Although these little organs have been observed on only four 

 species, it seems highly probable that they may prove to be 

 characteristic of the Poeciliidae, and hence of some systematic 

 importance. 



OCCURRENCE. 



Contact organs are found on all spawning males of the follow- 

 ing four species : Fundithis lieteroclitns, F. niajalis, F. diap/ianus 

 and Cyprinodon variegatus. 



They occur regularly in the following regions : 



1. On the rays of the dorsal and anal fins. 



2. On the ventral fins in Fundulus keteroclitus and F. diaphanus. 



3. On the margins of the scales of the sides, cheeks, snout 

 and top of head. In F. Jiiajalis they also cover the back from 

 the head to the dorsal fin. 



These are the regions in the males that come into most intimate 

 contact with the female during the spawning act proper or during 

 the preliminary courtship. Differences as to the details of the 

 distribution of these organs among the species are closely cor- 

 related with differences in the spawning attitude. 



In Fundnlus lieteroclitus the spawning takes place in pairs, a 



Contributions from the Zoological Laboratory, University of Texas, No. 97. 

 2 H. H. Newman, BIOLOGICAL BULLETIN, Vol. XII., No. 5. 



170 



