240 



Prof. H. C. Bastian on Heterogenetic 



[Mar. 21, 



separate living units fuse to form a new individual, the process is one of 

 mere fusion, and the product is similar in kind although necessarily larger 

 than its components. 



Similar mutual attractions, however, may be exerted by other living 

 Units when brought into close contact with one another, and the result 

 may be the formation of an aggregate in which considerable molecular 

 changes are compelled to take place. The products resulting from such a 

 fusion may be quite different from the originally fused units ; whilst they 

 will differ at different times according to the precise nature and number of 

 the units which enter into combination. Such processes are frequently to 

 be observed taking place in various parts of the " proligerous pellicle." It 

 is in this way, in fact, that those phenomena occur which make the name 

 "proligerous pellicle " suitable for the scum that forms on organic 

 infusions. The processes themselves come under the head of Heteroge- 

 netic Biocrasis. 



The first person who actually described the microscopical appearances 

 characterizing the evolution of higher organisms from the pellicle was M. 

 Pineau. This he did in 1845, in a memoir entitled " Recherches sur le 

 Developpement. des Animalcules Infusoires et des Moisissures" *. More 

 precision, however, was given to the subject in 1859, by M. Pouchet, when, 

 in his ' He'terogenie/ he described the mode of origin of some of the or- 

 ganisms which had formed the objects of Pineau's investigations as well as 

 of some different organisms. 



Although some of these observations have not been recorded with all the 

 details which might have been desired, yet I have satisfied myself that 

 the statements made by Pineau and Pouchet are substantially correct. The 

 observations of the latter have, moreover, been confirmed by MM. Joly 

 and Musset, M. Pennetier, and others. 



Nearly two years ago I described in ' Nature' f the mode of origin of 

 certain corpuscular organisms, and of some Fungus-germs, from differen- 

 tiated portions of the pellicle of hay-infusicns. These observations I have 

 since repeatedly confirmed ; and I now wish to describe other allied pro- 

 cesses, and the means by which I am enabled to obtain, almost at will, 

 either animal or vegetal forms from certain embryonal areas which are 

 produced in the pellicles of similar infusions. 



The characters of the pellicles that form on different hay-infusions of 

 the same strength differ notably, according to the temperature of the water 

 with which the infusions have been made ; and, to a less extent, according 

 to the mean atmospheric temperature to which they are subsequently 

 exposed. If the infusion has been prepared with very hot water (140° F. 

 and upwards), only a thin and somewhat tough pellicle will form, secondary 

 changes will take place in it very slowly, and they will lead only to the 



* See Ann. des Sc. Nat, (Zoologie), t, iii. p. 182 and t, iv. p. 108. 

 f ' Nature/ 1870, no. 35, pp. 172, 173. 



