10 Transactions oftlie Royal Microscopical Society. 



beautifiilly-formed oval bodies, as seen in Fig. 19. Its appearance 

 at this stage was extremely beautiful ; and subdivision being com- 

 plete, the oval bodies were in constant motion within. We were 

 quite unprepared for what ensued ; this object was carefully watched 

 for about two hours and twenty minutes, when the thin investing 

 membrane opened, and minute oval bodies, moving freely, and in 

 many of which a single flagellum could be seen, were set free. 

 The aspect of this emission when nearly complete is given at Fig. 20. 

 The growth of these emitted bodies was rapid ; but we could not 

 discover how the hooked flagellum first appeared. In some few 

 instances it was seen as in Fig. 21, before the hook had formed 

 upon it ; but its first appearance was unperceived. These minute 

 forms were watched through all the stages of growth until the 

 phenomenon of fission presented itself, and the cycle was complete. 

 But the union of tivo monads is not the only method. A union 

 of four, and even of six, has been on many occasions seen by us. 

 At Fig. '22 is a drawing of the blending of four, as seen in an early 

 stage. The blending in all essential respects proceeded as before, 

 only one eye-spot being developed at a. At length the sac-like 

 conditions presented themselves as at Figs. 23 and 24, PI. XL VIII. ; 

 when division ensued as at Figs. 25 and 26 ; when the multiple 

 internal segregation followed, as in the former case, reaching the 

 condition drawn at Fig. 27, and passing to that shown at Fig. 28, 

 when all was as before. In this case the details could be more 

 easily made out from the increased size of the object. 



We have here, then, a life history comparatively simple. 

 Fission is the most apparent mode of increase. This is preceded 

 by a diflerentiation of the part to be divided, characteristic of the 

 perfect monad; and by a marked amoeboid condition. By the 

 fission a reserved flagellum for future fission is apparently formed. 

 This may continue for many days, but eventually two, four, or even 

 six of these monads may unite together — take a flaccid sac-like form, 

 becoming quickly distended, and dividing internally into segments, 

 which go on subdividing until the sac is filled with beautiful oval 

 bodies which eventually escape, and are found to possess a single 

 flagellum ; these rapidly grow, acquiring in a manner not clearly 

 made out the second (hooked) flagellum, and when thus mature 

 recommence multiplication by fission. 



The effects of heat on the immature state of this form diS'er in 

 some striking particulars from the efiects of the same temperature 

 on the forms we have already described. The results of our experi- 

 ments on temperature, with all the forms examined, will be given 

 in our next communication. 



