312 Transactions British Mycological Society. 



teristics of the organisms from which it is derived, and from it 

 a new indi\'idual arises. From the fact that, in the higher 

 animals, this fusion of cells and nuclei is always necessary be- 

 fore any reproduction can take place, the sexual fusion was 

 regarded as an act of reproduction. 



But fertilisation is not an essential factor in reproduction. 

 It has been shown that eggs which under normal conditions 

 are fertilised can also develop without fertilisation if the male 

 gamete is replaced by some other agent capable of effecting the 

 necessary stimulation. Already in 1785, long before the mor- 

 phological characteristics of fertilisation had been established, 

 Spallanzani had tried to make use of such agents as electricity, 

 extracts of various organs of the body, dilute acids, alcohol, etc., 

 to stimulate the development of the egg in place of the seminal 

 fluid. His experiments were however unsuccessful, but in recent 

 studies of fertilisation on some of the lower forms of life it has 

 been found possible to induce at least the earlier stages of de- 

 velopment of the egg by other agents than that of the male 

 organ, and it is now well known that fertilisation may be in 

 certain cases replaced by stimuli of various kinds. 



Tichomiroff (1886) found that the unfertilised ova of the silk 

 moth could be stimulated to develop by rubbing them with a 

 brush, or dipping them for two minutes in sulphuric acid and 

 then washing them, and Loeb especially has given us since 1892 

 numerous examples of substances, hypertonic sea-water, solu- 

 tions of magnesium cliloride, sugar, potassium salts, inorganic 

 acids, calcium salts, fatty acids, etc.- — all of which are capable 

 of effecting division in non-fertilised eggs. 



In the conjugation of one of the Protozoa — Paramoecium — 

 which has been \'ery carefully studied by numerous observers it 

 has been found that although under normal conditions rejuven- 

 escence is brought about only after conjugation, it has been 

 found that rejuvenescence may be brought about by changes in 

 the culture fluids (Calkins), or may even be brought about 

 spontaneously, without conjugation (Woodruff). 



The obser\'ations of Woodruff are extremely interesting from 

 the point of view of the Fungi. He showed (1914, Jour. Exp. 

 Zool.) that the explanation of this spontaneous rejuvenation 

 without conjugation in Paramoecium aurelia is due to a nuclear 

 reorganisation in the individual cells which may be compared 

 to the nuclear reorganisation which takes place in conjugation. 

 The macronucleus breaks up and disappears, the micronuclei 

 divide twice, but the third division, which normally occurs in 

 conjugation, does not take place, a new macronucleus being 

 formed from the micronuclei, with ultimately a restoration of 

 the normal nuclear organisation. We have thus a nuclear re- 



