84 REPORTS ON INVESTIGATIONS AND PROJECTS. 



Dr. Hatai reports : 



Toward evening I saw one albino rat running swiftly in front of the 

 house, picking up some particles of food which I had thrown out. Later I 

 found several more albino rats running about at the back [south side] of the 

 house. The next morning I found one albino rat, whose ears were marked, 

 trapped at the back of the house, and one large female Norway rat along the 

 bank. During the night I heard several times the screaming of the rats in 

 front of the house, but could not determine which kinds of rats they were. 



It now remains to be seen if the white rats can survive the winter on the 

 Island. 



ADJUSTMENT TO CAVE UEE. 



The subject of adjustment to darkness is one that requires a long period 

 for its full elucidation. At the outset many special difficulties have had to be 

 met and overcome. We have had the difficulty of carbon-dioxide in the 

 water, of solution of lime from the concrete tanks, and of the growth of 

 fungi in the darkness of the cave. The difficulty of carbon-dioxide in the 

 water of the artesian well will require the construction of a settling basin 

 containing growing plants. Such a basin will be advantageous also, inas- 

 much as it will form a natural breeding-spot for the small organisms that 

 can be used by the cave fishes. Dr. Banta spent two months last winter in 

 the cave region of southern Indiana collecting materials and working on 

 problems connected with cave-life. In order that parallel experiments may 

 be run with cave animals in the light, a vivarium was constructed at the 

 north end of the main building to provide conditions like those of the arti- 

 ficial cave except for light. It is provided with hot water pipes for winter 

 heating, and being on the north side of the building will be largely sheltered 

 from the summer sun. 



Already the amphibia reared in the cave have yielded interesting results. 

 The tadpoles of Amhlystoma tigriniini, the common salamander of our 

 ponds, when reared in the light are black, but in the cave are "white" or 

 nearly so. The light is necessary for the production of the body pigment in 

 the developing tadpole. 



A part of Dr. Banta's work is the light reactions of animals of which 

 related species or individuals live in the cave and in the open. While in 

 Indiana he worked on the light reactions of the amphipod Bucrangonyx 

 gracilis of Mayfield's cave and on the outdoor forms of the same species that 

 live abundantly in the surface streams of the same region. Studies have 

 also been made on the feeding and breeding habits of Asellns and other 

 invertebrates which it is desired to propagate in the cave. 



The following non-cavernicolous species are now kept in the cave : Hydra, 

 Copepoda, Asellus communis, Oniscus asellus, Armadillidium vulgare, Por- 

 cellio scaher, Porcellio rathkei, Bucrangonyx gracilis (surface form), Gam- 

 marus fasciatus, Camharus bartoni, Meta menardi and other spiders, Thy- 

 sanima, Ceuthophilus, Planorhis, Limnea, goldfish, sunfish. Umbra limi, 



