132 Transactions of the Society. 



though, as he says, " my teeth are kept usually very clean," he 

 tried other people's mouths, from that of a baby one year old to 

 that of an ''old man and a good fellow," who was not very parti- 

 cular, and he found them in all ; in the latter, the material " seemed 

 alive." He notes they were not killed " by the parties continual 

 drinking brandy, wine and tobacco," although he could kill them 

 with wine- vinegar outside the body. He could not see them in 

 ordinary saliva ; but he describes similar organisms, and especially 

 leptofchrix, in the fur from the tongue, in which he also found 

 epithelial scales. 



He first saw and described the yeast organism in 1675, and 

 he also describes some common moulds, and their method of 

 growth which he watched, and he describes the growth of spores. 

 He says : " this knob " at the end of one of the branches " indeed 

 consists of nothing else than of many small roundish knobs, 

 which being multiplied, the big knob begins to burst asunder." 



He also discovered Eotifers, and showed " how wonderfully 

 nature has provided for the preservation of their species," both 

 by their tolerance of the drying up of the water they live in, and 

 by their casing preventing the evaporation of their body fluids. 

 He saw the first Foraminifer in the stomach of a shrimp, and 

 completed this branch of his life-work by the discovery of the 

 Infusoria. He found them first of all in rain-water — four sorts 

 are described in his first paper on the subject — but when he 

 collected it with care and examined it at once, none were found. 

 He also found them in his well-water, and very few in the canal- 

 water of his native town (Delft is even now famous for its extra- 

 ordinarily clean canals). He found them in sea- water and in large 

 numbers in an infusion of pepper in water. He found none in 

 snow-water kept in a perfectly clean bottle for three years, but 

 on putting pepper into this, they developed in large numbers in 

 ten days, and he found that cold arrested their growth. All these 

 circumstances went to show that none of these organisms were 

 produced by spontaneous generation. 



He knew how water became infected with these organisms, 

 for he says : " We can now easily conceive that in all rain-water 

 which is collected from gutters in cisterns, and in all waters 

 exposed to the air, animacules can be found ; for they may be 

 carried thither by the particles of dust blown about by the winds." 



His work on Spermatozoa was very remarkable, and he was a 

 very strong opponent of the theory of spontaneous generation. 

 Although he did not discover Spermatozoa (they had been seen by 

 Hamm a few months earlier, though not described) he was the 

 first to see and describe them with any accuracy, and in many 

 animals, such as the dog, hare, fish, birds, and insects. He thought 

 they were a kind of homunculi, for he says : " I take them to be 

 made of as differing parts as all other animal bodies." In a hare 

 he found them moving four days after death, and he knew they 



