190 HETEEOGENETIC CHANGES IN 



or eight days, be then converted into Fungus-germs rather than 

 into Monads. It is difficult to be certain of this, but I am strongly 

 disposed to beUeve that it is so. It is quite certain, however, that 

 conversion into Monads, when it occurs, takes place almost always 

 somewhere between the third and the fifth days, while after the 

 latter date, up to the tenth or twelfth day, one finds Zooglcea 

 masses either all brown or producing brown segments which are 

 being converted into Fungus-germs. But the Zooglcea masses, and 

 all the segments into which they divide, invariably remain colourless 

 where Monads or Amxbce are to be the products. 



Since my recent communication to " Nature " (Nov. 24, 1904) I have 

 seen numbers of the Zooglcea masses yielding Monads in the pellicle 

 on an infusion of hay, which was exposed to light in a small beaker. 

 The Monads were met with on the fourth and fifth days, the 

 temperature, to which the infusion had been exposed, having varied 

 from about 54°-S9° F. (i2°-i5° C). The Zooglcea masses were 

 in many cases very large and presented some peculiar characters. 

 In their early stages they always appeared as very pellucid, some- 

 what ramified, discontinuous areas, such as are shown in Fig. 19 

 (x 500) ; A represents an early, and B a later stage in which 

 separation of ultimate segments is commencing. Still later stages 

 are shown in Fig. 20 (500) : portions of the mass beginning to 

 segment may be seen on the left, while above and to the right, a 

 more complete segmentation into motionless, colourless units is seen, 

 which after a time may become either active, flagellate Monads, or 

 Amcebse — sometimes the one and sometimes the other of these 

 convertible forms of life. A similar process taking place in other 

 small Zooglcea masses, is plainly shown in Fig. 21 (x 500) : thus in 

 A we have small masses of Zooglcea in which the constituent 

 Bacteria are plainly seen ; in B other masses becoming more 

 refractive and about to segment ; while in C segmentation is actually 

 occurring, and the products are still more refractive. They, as 

 well as the products in Fig. 20, are destined to develop either into 

 Monads such as are shown in Fig. 24, E (x 500) or else into 

 minute Amoebae of the same size. 



Since the last two paragraphs were written I have made some 

 observations, very interesting in many respects, but especially so 

 from the point of view of the existence of an interchangeable 

 relation between Monads and Amoebae on the one hand, and 

 Fungus-germs on the other, to which I have previously referred. 

 These observations were of the following nature. 



