Some ants' nests were placed under a bell jar and supplied with leaves; they made no use of them and presently died. If they were supplied with a piece of "garden," they rebuilt it and covered it so far as they could. It was seen to shrink from day to day, the ants bringing out the old pieces and adding them to the wall; finally it was exhausted and the ants died. Others were starved for five days, and then supplied with a bit of garden; they at once began to eat the Kohl-rabi clumps. Finally, by supplying the ants with bits of garden, a damp sandy floor, and fresh leaves, they were induced to build in captivity. The dish in which they worked was covered by a glass lid, and when this was covered with a dark cloth or otherwise kept dark, the ants built under it without covering the garden. In this way the whole process was observed. An ant bringing in a piece of leaf proceeds to cut it into halves, repeating the process till it has got a very small piece left, which it holds between its fore feet and turns round, crushing it in its jaws until the whole is reduced to a round ball of pulp about .25 mm. thick. This it then takes and adds to the garden. So well is the kneading performed that no single cell remains uninjured, and it was observed that the hyphae of the fungus grew through and round one of these particles within a few hours. Belt supposed that this process was performed by the small workers above-mentioned, but it is not so, as we have just seen. The small workers perform the function of weeding the garden, and this is so well done that a portion of it removed and grown in a nutrient solution gives a perfectly pure culture, not even containing bacteria! In the course of these investigations it was found that somewhat similar fungus gardens occur in the nests of the hairy ant, _Apterostigma_, but the fungus appeared to belong to a different genus, and the hairy ants, who live in decaying wood and have small gardens built of bits of wood-fibre, beetle-dung, etc., have not succeeded in cultivating and selecting Kohl-rabi to the same high degree. An allied genus of ants, _Cyphomyrmex_, were also found to be fungus-growers. This elaborate study, which is illustrated by beautiful plates and photographs of the mushroom gardens, constitutes, as Mr. Willis (whose summary has here been followed) remarks, one of the most fascinating contributions to our knowledge of mycology and of animal industries which have been made for many years. INDEX.