768 



SCIENCE 



[N. S. Vol. XXXII. No. 830 



dilution, to get tlie same degree of dilution 

 the chlorides would be reduced from 6.041 to 

 5.631 grams per 1,000. As a matter of fact, 

 the actual amount of chlorides found was 

 4.132 grams per 1,000 or 27 per cent, less 

 than if it were a case of simple dilution. 

 Again applying the same method to the third 

 sample, if it were a case of dilution alone we 

 should expect 5.324 grams per 1,000 grams 

 blood, whereas analysis shows but 3.590 grams, 

 or about 33 per cent, less chlorides than if it 

 were a case of simple dilution. The salts 

 would not disappear in the tissues, for if any- 

 thing the tissues would be surrendering their 

 salts to the blood stream in an endeavor to 

 keep up the osmotic pressure of the blood. 

 We are therefore forced to conclude that the 

 chlorides passed out through the gills — in 

 other words, the gills are permeable to salts. 



G. G. SOOTT, 

 College of the City of New York 



G. r. White, 



Richmond College (Virginia) 

 '■ PEDOGENESIS IN TANYTAESUS 



As the phenomenon of pedogenesis in the 

 Chironomidse is rarely observed, it may be of 

 interest to zoologists to know that we have a 

 species of rather wide distribution in which 

 this mode of reproduction seems to be of com- 

 mon occurrence. In the summer of 1903 at 

 Ithaca, New York, while studying the 

 Chironomidse, I several times came upon the 

 larva of Tanyiarsus dissimilis, which, when 

 placed in a tumbler of tap water gave rise to 

 a number of individuals. The same year the 

 late Dr. Fletcher, dominion entomologist, 

 sent me some adults of the same species for 

 identification which he said had developed 

 psedogenetically. 



This summer at Orono, Maine, I found a 

 number of them in a jar in which some Dixa 

 larvffi were kept. They appear to have been 

 the progeny of a larva introduced by chance. 

 One individual of this generation after care- 

 ful examination was transferred to another 

 jar containing distilled water, a bit of steril- 

 ized vegetable debris serving as food. These 

 precautions were taken in order to prevent 



eggs or small larvse being carried over. After 

 about two weeks a number of minute trails 

 were observed, each containing a young Tany- 

 iarsus larva, a new generation appearing 

 simultaneously also in the first jar. Though 

 I have reared many species of Cliironomidm, 

 I have never observed this method of repro- 

 duction in any other species. In this connec- 

 tion it is interesting to note that Professor 

 Zavrel quite recently ('07) published an ac- 

 count of pedogenesis in Tanyiarsus occurring 

 in Bohemia. It is quite possible that the 

 species with which Grimm worked also be- 

 longed to the same genus. 



The larvffi are usually to be found in the 

 mud and sediment in pools where Anopheles 

 might live. Jars containing cultures of Pro- 

 tozoa are sometimes seen with a number of 

 the characteristic trails or tubes of Tany- 

 iarsus larvae on the sides of the glass. The 

 tube is composed of fragments of decaying 

 plant tissue and is usually several times longer 

 than the larva which inhabits it. If the tube 

 be disturbed the insect wriggles out and 

 swims away by violent contortions of its body. 

 When full grown it is about 3.5 mm. long, of 

 a pale amber color and is readily distinguished 

 from other related forms by its relatively 

 long, non-retractile antennte and the form of 

 its mouth parts. The pupa is characterized 

 by the arrangement of the setae on the dorsum 

 of the abdominal segments, most readily seen 

 in a cast skin. The adult is about 1.5 mm. 

 in length, yellowish-green in color with 

 three brovsoi thoracic stripes, and though com- 

 mon enough, owing to its small size is but 

 rarely seen. More extended descriptions of 

 the three stages may be found in Bulletin 86, 

 New York State Museum (1905). 



I have long delayed publishing my notes on 

 this insect thinking that I might sooner or 

 later chance upon larvae in which the young 

 were developing, but as lack of time prevents 

 my making a systematic search I now write 

 this in the hope that it may put someone else 

 upon the track of this interesting species. 

 o. a. johannsen 



Maine Ageicultueal 

 ExPEEiMENT Station 



