394 PROGRESS OF SCIENCE IN THE CENTURY. 



by Dr. H. M. Vernon.* (2) Heape is responsible 

 for a number of experiments ou artificial insemina- 

 tion, and for such daring experiments as the follow- 

 ing, f From an Angora doe rabbit (fertilized 32 

 hours previously by an Angora buck) he transferred 

 two ova into the upper end of the oviduct of a Bel- 

 gian doe rabbit (inseminated three hours previously 

 by a Belgian buck), with the result that when the 

 Belgian doe gave birth, four of the young were 

 Belgian and two Angoras. (3) Prof. Cossar Ewart's 

 " Penycuik Experiments " have added not a little 

 to our knowledge as to the variable results of hybri- 

 disation and as to the occurrence of reversions.^: 

 (4) The experiments of Ritzema-Bos and others 

 as to in-breeding (in rats) suggest that there are 

 limits beyond which this is likely to prove very dis- 

 advantageous. 



(5) Of the utmost importance, as indeed a be- 

 ginning of an experimental study of the conditions 

 of reproduction in plants, has been the careful work 

 of Klebs (1896), in which he has shown how changes 

 in the environmental conditions may induce, in 

 Algse and Fungi, the occurrence of sexual or asexual 

 reproduction. The factors investigated were nutri- 

 tion, moisture, light, temperature, and chemical re- 

 agents ; and the general result is a proof that certain 

 external conditions determine the occurrence of asex- 

 ual reproduction (by zoospores), while others aa 

 certainly evoke sexual reproduction (by gametes). 



(6) Maupcu' Experiments. Though the work of 

 Haupas, like that of Klebs, has chiefly to do with 



Proc. Roy- Soc. London, LXV. (1899), pp. 350-360. 

 t Proc Roy. Soc., London, XLV1II. (1891), pp. 457-58. 

 I The Penycuik Experiment*, 1899. 



