108 



In fact, the respiration takes place in quite the same manner as in the case of the 

 Donaciin larva', the life of which has been so admirably studied by my friend Dr. Ad. 

 Boving in almost the very same locality where the Tceniorhynchus larva was found. 



Till 1914 the .l/rt/!.soma-larva? have only been found in America, and as I knew 

 that the genus Tceniorhynchus (= Manspnia) has an almost entirely tropical distri- 

 bution, it will be understood I could not have been more astonished even if I 

 had drawn forth a representative of the Dipnoi from the mud of the Donse pond. 



In the autumn of 1914 I made many excursions to Donse, and I found many 

 larvae. Frequently I had 30 — 40 larva? in my aquaria, where I had ample opportu- 

 nity of seeing the larva? creeping between the roots and piercing their tubes into 

 the plant-tissues. In one of the last pages of my paper on the Aquatic Insects I 

 gave a microphoto of the larva fixed to a root, and some drawings of the tracheal 

 system and the sipho. 



The larva was rare; the greatest number I was able to procure after searching 

 for 4 — 5 hours was 10 — 15. Strangely enough I could never find it in any other 

 locality than where I had found it the first time. The vegetation was composed 

 of Acorus, Ranunculus lingua, Glycerin spectabilis and Typha angustifolia. I have no 

 impression that the larva preferred any of these plants to the others; if so it would 

 probably be Acorus. In the aquaria the larva fastened itself to the most different 

 plants and often sat for a fortnight or more fastened to the same spot. It was al- 

 ways restricted to very shallow water. I never found it deeper than Vs meter. The 

 best method to gel the larvae is to loosen the roots of the plants from the bottom 

 and then to shake them in high cylinder jars. When the material has sunk to the 

 bottom the larvae will be found creeping slowly over the decaying material. More 

 than once on examining the plants I saw the animals fixed in their normal position, 

 trying to detach themselves when the plant was brought onboard. I have never 

 found more than two or three on one plant. Altogether I have probably caught 

 about 100 larva?. 



It was my intention to keep the larva? during Ihe winter in my laboratory, 

 but in February they all died, probably because I had kept them at too high a 

 temperature. As soon as the ice on the pond had melted I went again to Donse to 

 procure fresh material. Behold, another great astonishment, though not so agreeable 

 as when I found the larva?. An enterprising man had bought the water in the ponds 

 with the intention of establishing an electricity works at the little brook. The still- 

 born project supplied the country with electrical light for some months, and the 

 water of the pond disappeared. Next year it was almost wholly dried up; not a 

 single larva was to be found, the water having receded far beyond the zone where 

 they lived. On summer evenings I lay in the grass, hoping that some mosquito, 

 new to our fauna, would come and suck my blood. All was in vain. Neither in 

 1915 nor in 1916 did the water reach the zone where the larva? were found in 

 1914. As long as the imago was not found, I did not like to publish my observa- 

 tions. 



