Juke 21, 1918] 



SCIENCE 



619 



males to 100 females). In the B series, on the 

 other hand, selection preserved the females in 

 which the ova tended to attract "female-produc- 

 ing" spermatozoa, consequently the series showed 

 an excess of females (81.8 males to 100 females). 

 The results indicate that it may be possible to 

 swing the sex ratio in a desired direction, even 

 though we are unable to determine the ultimate 

 cause of sex itself. 



The Kaiades of the upper Tennessee drainage: 

 Aknou) E. Ortmann, Ph.D., Sc.D., professor of 

 physical geography. University of Pittsburgh. The 

 upper Tennessee region (above Chattanooga) has 

 long been famous for the great number of mussel 

 species found in its water. It has been studied by 

 various collectors for nearly one hundred years; 

 but up to the present time great confusion pre- 

 vailed as to the species found in this region, and 

 their afltaities. The present writer made it his 

 chief object during four summers, to collect the 

 shells of this drainage together with the former; 

 this is imperative for a proper understanding of 

 all Nayad shells. It was found that the material 

 collected included practically all species previously 

 reported; it was possible to ascertain, in every 

 case, the proper systematic position of each form, 

 and, finally, the geographical distribution of each 

 form, within this area, was ascertained, and was 

 correlated with the geographical range elsewhere. 

 Thus, the present paper represents a complete ac- 

 count, a synopsis, of everything known hitherto 

 about the upper Tennessee mussels and with nu- 

 merous additional observations not known previ- 

 ously. 



A new type of insect larva: William Morton 

 Wheeler, Ph.D., Sc.D., professor of economic ento- 

 mology, Bussey Institution, Harvard University. 

 The first larval stage ("trophidium") of two 

 African ants, Pachysima wthiops Smith and P. 

 latifrons Emery, proves to be unlike the larva of 

 any known Formicid or, in fact, of any known in- 

 sect, in possessing peculiar exudate organs ("eiu- 

 datoria") surrounding the mouth. These organs 

 are very primitive adipose glands which evidently 

 furnish a liquid agreeable to the worker ants and 

 are very similar to the exudate organs of ant 

 guests (myrmecophiles) and of termites and their 

 guests (termitophiles). The salivary glands and 

 fatbody have a similar function in other ant larvte. 

 The relations between ants and their larvm there- 

 fore involve mutualistic or reciprocal feeding and 

 this accounts for the development of the colony both 

 ontogenetically and phylogenetically and therefore 

 for the social habit of the Formicidse. Myrme- 



cophily, trophobiosis, "social parasitism" among 

 the ants themselves and the relations of ants to 

 plants with extrafloral nectaries and food bodies 

 all depend on essentially the same conditions. 

 Similar conclusions are reached in regard to the 

 origin and meaning of the social habit among so- 

 cial wasps, some bees and termites. 



A critical survey of the sense of hearing in 

 ]is}tes: Georoe H. Parker, Sc.D., professor of 

 zoology. Harvard University. That fishes could 

 hear was maintained by most of the naturalists of 

 antiquity, such as Aristotle and Pliny. This was 

 also the opinion of such masters of the art of fish- 

 ing as Isaac Walton and of such students of fish 

 anatomy as John Hunter. In fact this was the 

 universal view of the function of the ears in fish 

 till 1878 when von Cyon declared that their only 

 function was to keep the fish in equilibrium. This 

 opinion was supported by Kreidl, who in 1895 at- 

 tempted to show that when fishes did respond to 

 sounds they responded through the organs of touch 

 and not through the ear. Following Kreidl 's work 

 appeared a series of researches some of which sup- 

 ported the opinion that fishes did not respond to 

 sounds at all while others tended to show that fishes 

 did respond to sounds and that this response was 

 mediated by the ear as well as by the skin. One of 

 the most sensitive fishes in this respect is the com- 

 mon catfish Amiurus. Tests on this fish were car- 

 ried out by Parker and Van Heusen with the fol- 

 lowing results. In catfishes in which the ears had 

 been destroyed, the skin was found sensitive to the 

 dropping of water, to water currents, to a slow 

 vibratory movement of the whole body of water, to 

 the impact of a leaden ball on the slate wall of the 

 aquarium, but not to a whistle blown in the air. 

 In catfishes in which the skin had been rendered 

 insensitive, the ear was stimulated by a slow vi- 

 bratory movement of the whole body of water, by 

 the impact of the leaden ball, and by a whistle 

 blown in the air, but not by the dropping of water 

 nor by currents of water. To test more fully the 

 effects of sounds, catfishes were subjected to the 

 tones from a telephone contained in a tight rubber 

 bag and submerged in the water of the aquarium. 

 When the ears were destroyed, the catfishes re- 

 sponded to vibrations 43 to 172 per second but not 

 to vibrations 344 to 2,752. When the skin was 

 rendered insensitive, they responded to vibrations 

 43 to 638 but not to vibrations 1,376 to 2,753. 

 Catfishes respond, therefore, to a range of low vi- 

 brations less freely through the skin, more freely 

 through the ear. Hence they have unquestionable 

 powers of hearing. 



