OF CERTAIN TERMITE NESTS. 247 



nest with fresh spores. Moller states that the leaf -cutting ants 

 carry their fungus garden to a new nest, but the possible modes 

 of establishment of new colonies by termites do not favour the 

 supposition that a similar transference takes place in their case. 

 Yet on the present evidence they could not obtain the agaric 

 or "spheres" elsewhere : these have not yet been found apart 

 from termite nests. 



Assuming this supposed sterilization, there then arises the 

 difficulty of maintaining a pure culture. Mites are quite effi- 

 cient in introducing fungus spores into agar cultivations, and 

 it is extremely unlikely that no spores should be similarly taken 

 into the comb by the workers and soldiers. A system of weed- 

 ing appears to be necessary to keep out other fungi, and it 

 seems probable that Xylaria (nigripes ?) is the one species 

 which is kept under but not exterminated by this process. 



Holtermann (7) states that in spite of all precautions Mucor 

 and Penicillium appeared after one or two days on combs 

 placed in crystallizing dishes. He considers that the spores are 

 originally present in the comb, but are only able to develop 

 under the altered conditions, and attributes the purity of the 

 termite cultivation either to the fact that these foreign fungi 

 cannot develop underground or that the termites adopt a 

 system of weeding. The latter he considers improbable, since 

 " if the comb before it is put in the dish is full of living termites, 

 the growth under the influence of light still commences." This 

 objection loses force when it is remembered that this growth 

 is that of the Xylaria stromata, and that as previously stated 

 these are constantly eaten off as long as a comparatively small 

 number of termites is present. If the normal population 

 . could be retained, there would be no growth of Xylaria. 

 It will be shown later that for two forms at least Holtermann' s 

 first supposition is incorrect : other fungi than the agaric, 

 spheres, and Xylarias can develop on the comb below ground. 

 Doflein (13) also remarks on the purity of the comb culti- 

 vation, but rejects the idea that it is due to the weeding out of 

 foreign fungi : he suggests that the digested wood forms 

 9(8)06 (20) 



