250 



Prof. H. C.Bastian on Heterogenetic 



[Mar. 21, 



solution. Changes of an unhealthy nature seemed to have been so suddenly 

 induced that the organisms did not possess sufficient energy even to undergo 

 the process of encystment. Their own molecular movements (those which 

 pertain to the ordinary life of the Amoebae) being so languid, other retro- 

 grade changes were initiated, leading to the birth of new particles through- 

 out their substance. Bacteria, in fact, were generated by a most typical 

 process of secondary evolution. 



The changes which have been thus observed constitute a very remarkable 

 series. The simplest living units {Bacterid) first swarm in the infusion*; 

 these become aggregated at the surface so as to form a " proligerous pel- 

 licle," in which embryonal areas gradually appear : as a result of segmenta- 

 tion in these embryonal areas, specimens of Monas lens, -g-^- in diameter, 

 more or less suddenly make their appearance ; they increase in size, occa- 

 sionally assume an amoeboid appearance for a time, and are ultimately 

 transformed into real Amoebae. The transition is effected by the loss of the 

 flagellum, the appearance of vacuoles in their interior, and the simultaneous 

 manifestation of polymorphism and a creeping mode of progression ; at the 

 same time a nuclear corpuscle develops in the interior, and the whole animal 

 grows considerably. At last the Amoebae gradually cease to exhibit their 

 characteristic movements, whilst they become more or less spherical and 

 motionless. Ultimately a firm bounding membrane is produced, and they 

 pass into the encysted condition, in which, although slightly smaller in size, 

 they constitute spherules yg^o"" in diameter. On the removal of some of 

 this pellicle to the surface of a fresh infusion, the Monads and Amoebae 

 greatly increased in size ; all the Monads gradually became converted into 

 Amoebae, and some of these at first went through the ordinary process of 

 encystment, though at last (on account of some more sudden change in the 

 fluid) they seemed suddenly to lapse into a morbid state. They were ap- 

 parently unable to encyst themselves ; and not being capable of continuing 

 as Amoebae, there sprang up in their interior a teeming progeny of new 

 units (Bacteria), the production of which occasioned the final dissolution 

 of the organisms in which they were evolved. 



Other changes, however, took place in this same infusion which deserve 

 to be chronicled. On the sixth day there were seen scattered throughout 

 those portions of the pellicle intervening between the embryonal areas a 

 multitude of solitary spherules, varying in size from mere specks 30 ^ 00 " in 

 diameter, or less, to bodies q" in diameter. They were colourless, quite 

 motionless, and appeared to be solid and almost homogeneous masses of 

 plasma rather than vesicular bodies (fig. 4, a). There were merely faint indi- 

 cations of granules in their interior, and no evidence of a differentiated outer 

 membrane. None of them seemed to be undergoing processes of self-division, 



* Although I do not, in the present communication, touch upon the mode of origin 

 of these simplest living units, this question has been pretty fully considered in my 

 ' Modes of Origin of Lowest Organisms,' 1871. 



